Mechanics 082019



 ? Cover Foxhole? Cover Foxhole

In many ways, the humble foxhole is simply a smaller-scale trenchwork intended for shorter term use or occupation than a proper trench, series of trenches, or any other fortification.  They can be dug by any soldier with a proper set of field-gear can dig a foxhole that would easily hold them in reasonable ? cover within 1 day of continuous work.  To create a foxhole that would provide ? cover would take 2 days of continuous work.  Foxholes can only contain 2 individuals at a time within their cover at a maximum.  A foxhole will begin to degrade within roughly 6 months of disuse or lack of maintenance.  

     ? Cover Foxhole with ? Cover Sandbags           ? Cover Foxhole with ? Cover Sandbags

If a ? cover foxhole is used in conjunction with ? cover sandbags, the improvised structure can provide ? cover.  If a ? cover foxhole is used with ? cover sandbags, the improvised structure can provide full cover against incoming fire.  

If four more hours are spent on concealing the improvised structure (after which point no additional modifications can be made) the foxhole will require a DC18 perception check to be spotted.  This is reduced to a DC16 perception check if within 100m or if the area is viewed through an optic.  When a concealed foxhole is fired from, the perception check is reduced to a DC14.  If the foxhole is fired from more than once within a one minute period there is a a further -2 to the DC14 per shot fired within a minute.  Upon failing its check to remain concealed the foxhole is discovered by a member of the opposing forces, who can relay the area to their nearby allies.


By and large the single most common set-piece feature of many of the battlefields in Trenches and Alchemy will be the first components of its very name- trenches.  Trenches are fortifications made by digging into the ground below them to create firing positions, means of transportation, communication, and any other number of pieces of infrastructure that are more-or-less hidden from enemy view for the most part and allow for a strong defensive position to be held.  Strong against both direct and indirect fire, trench warfare is largely defined by the incredible advantage that is held by those who maintain the trenchline while an attacker attempts to storm it.  Furthermore, oftentimes such lines are fully intended to have multiple phases or fallbacks, and are ‘weakened’ to assault from one side by design to ensure that taking an enemy trench is much less advantageous than one would hope.

Trenches most-often provide at least ? cover to those within them .  Specifically made firing positions with additional cover, or pillboxes or other ‘harder’ fortifications provide ? cover in most circumstances.  Deep trenches might provide full cover, though it is entirely dependent upon their location and their intended use.  Trenches are, unless otherwise noted, largely ‘open’ constructions without components to provide any cover overhead.  This often makes conditions within them muddy and rather miserable to those who are making do with such conditions unless significant engineering has gone into ensuring that a multitude of basic needs are being met and that the trench has been made with accommodating those in mind.

         The universe’s most sterile trenchlineTrenchline with firing positions and a pillbox

Trenchline with firing positions, pillbox, concertina wire,

some limited supplies stored in trench, mess area, cooking area…

Trenchlines can be as simple, or as complex as makes the world truly immersive for the players.  Simple lines exist for the sake of simply pushing back the enemies.  But some positions have become very nearly traditional ‘forts’ in the amenities and things that they have come to offer up to those stationed within.


Large-scale constructions of concrete that are often underground or at least making use of natural earthworks as defenses potential attacks from outside of the structure.  Made to withstand direct hits from a great many weapons that would otherwise pose a threat to the occupants or the objects that are held within.  Frequently, when not merely being used in the capacity to hold a squad, a munitions magazine, or some other smaller-scale objects or group of personnel pillboxes are merely the entrances to larger underground complexes and bunker networks which might supply a vast portion of a trench-line with unimpeded movement and/or access to supplies that would be vulnerable even in the protection of a trench.


Poison Gas

Seeps into trenches, and will incapacitate or outright kill those who have been exposed to the substance(s) that they are composed of without discrimination if they are not wearing the appropriate gas-masks.  Method of death, damage, or the cumulative damage of subsequent exposure(s) may manifest themselves in vastly different ways depending upon the types of poison gases being deployed to the battlefield.

White Cross

The least lethal of all variants ‘white cross’ marked shells are all but harmless to those who have donned protective masks. These masks can sometimes even be made of relatively easy-to-scavenge materials without much knowledge of the components or of their properties.  Merely soaking rags in water and wrapping them around the nose and mouth sometimes being enough to stave off the worst of the effects.  They act as temporary respiratory irritants and are generally regarded and exceptionally annoying and unpleasant to deal with, however are rather least amongst the threats.  The only reported casualties to such substances have all been reported as being of exceptionally unsound lungs prior to their excessive exposures to the compounds in White Cross Gases.

Yellow Cross

A more-lethal variant of substance, a Yellow-Cross gas is delivered by any of a variety of means to the lines of an enemy with the intent of incapacitation of the occupants of the area.  It is not generally used only to screen an assault or to provide an additional method by which to produce the general ‘shock and awe’ tactics of breaking into a trenchline, but of weakening the line itself.  These gasses can linger anywhere from mere hours to weeks depending on the conditions and on the substances which are used and classified as such.   Direct exposure to high concentrations can often lead to skin damage.  Prolonged exposure can generally lead to lethal complications with most, if not all Yellow-Cross rated gasses.  Merely covering the mouth and nose with salvaged materials will not function as adequate protection given other mucus membranes.  These gasses can often be seen visibly, and given how more than a few breaths exposure for such can occur prior to the effects of many will give more than enough time to allow for proper protection or distancing oneself from the vicinity based on the circumstances.

Red Cross

Red-Cross gasses share a majority of their purpose and use with Yellow-Cross gasses.  They are intended to kill outright or to incapacitate the occupants of a trench through chemical means.  However, they differ in the most-important aspect which makes Yellow-Cross gasses somewhat less impressive in the eyes of many besides as a single part of a shock and awe tactic.  That being that most are colorless, and as close to odorless gasses as is possible.  While several Red-Cross gasses do have some scent or vague impression in the air, unlike White or Yellow-Cross gasses they are distinctly meant to provide as little warning as possible to inflict as many casualties as possible on an enemy’s line.  After being fired, in many cases it is entirely impossible to know when the gasses have entirely dissipated in trenches or in the open in any major depressions.  


Incendiary weapons in warfare are hardly something new, but the world of Trenches and Alchemy is beginning to see the advent of warfare using various flammable substances at range and in quantities that would have only been dreamed of previous to the modernization of both alchemy and general technology.  Fire can be used to control the battlefield in many ways… but of course, once unleashed can certainly end up controlling the battlefield to the detriment of even those who unleashed it.

Slow-Burning Fuels

Incendiary weapons with slow-burning fuels are rarer, and include those weapons which will burn for well over a minute and impact the flow of battle in somewhat more ‘pronounced’ a way than weapons that can merely be deployed by infantry.  Sometimes burning with more or less intensity than the more common fast-burning fuels, they present a near-constant hazard to those on the battlefield who might be near them while they continue to blaze.

Fast-Burning Fuels

Incendiary weapons with fast-burning fuels encompass most of those found on the battlefield and employed in infantry-deployable roles.  They encompass weapons like flamethrowers, incendiary grenades, and any improvised method of creating fire on a reasonably small-scale which might last for under a full minute once ignited.  Generally, these fuels can be found in relative abundance, and though they burn exceptionally hot can be quenched by either weather conditions or by a concentrated effort on the side of one party.  These weapons can be used to help control the battlefield only very temporarily, and while they may impact an area for time-to-come are incomplete in their destruction of most objects within the area with any reasonable amount of structural stability.

Set-Piece Weapons

4.2cm Guns

The largest caliber allowable on the field as a ‘small gun’ following a number of treaties and agreements made around the world of Trenches and Alchemy, the 4.2cm field-gun is found in almost each and every military serving in much the same capacity.  A massive weapon capable of firing ingressed rounds of a variety otherwise unmatched save by artillery pieces.  They are a terror to the battlefield, and when unpacked and manned by a trained crew can outdistance most infantry weapons by a significant amount.  Furthermore, with their heavy platform they can fire more accurately and can even reasonably take on the same role as a ‘sniper’ with a trained gunner against even hardened positions.  These weapons have become important targets in most military scenarios.  The be destroyed prior to being set up in the first place or at least prior to them weakening a line enough for the enemy to feel secure in ordering an assault section over-the-top.

Mechanically these weapons act with stats as set out in the bestiary.

205mm Guns

The most common artillery caliber, the 205mm artillery gun is a main staple of many nations in breaking enemy lines through sheer force.

Combat Systems


The importance of cover in trench-warfare is exceptional when taking into account the simple fact that so many of the weapons being used are ranged and can do so much damage with even a glancing blow.  There are four general states in which any creature can be in as regards cover.  Having no cover, having half cover, having three-quarters cover, and having total cover.

No cover is a state that can be considered as the simplest and perhaps as the default state for the general rolling of attacks.  No modifications will be made to rolling for attacks against any target which as regarded as having no cover.  The state is simply achieved by the target creature or object being more than half in-view.  Not obscured by any trench, fortification, or other form of cover or concealment.

Half cover is something that is achieved by a creature or object being at least half, but less than three-quarters obscured by some form of cover.  This state gives the creature or object a +2 AC against firearms as well as a +2 to any saving throws by a projectile damage weapon.  This can be achieved reasonably with most types of fortifications, even those that have been improvised if one were to crouch or use the available cover to the best of their abilities.

Three-quarters cover is something that is achieved by a creature or object being at least three-quarters but less than fully obscured by some form of cover.  This state gives the creature or object a +5 AC to firearms as well as a +5 to any saving throws by a projectile damage weapon.  This is most often achieved when standing within specific positions within a trenchline.  Firing positions that specifically leave few vulnerabilities, well-made fortifications like pill-boxes with firing slits, or other such types of cover that leave little exposed to attackers.

Full cover is being completely and utterly obscured by cover in a direct line of sight.  It makes it impossible to fire on the creature or object with any reasonable degree of accuracy.  If a creature wishes to attempt some sort of attack to any other creature or object through such a cover the creature or object would have a +10 AC and a +10 to any saving throws by a projectile weapon.  Furthermore, any damage output would be reduced by ?.  In the event that such cover does not also have a roof, certain weapons can still be used with reasonable accuracy to go over such cover and to potentially damage those behind it with area of effect damage.  Similarly, area of effect weapons can be thrown to the side of such cover to the same effect.

Combat Rounds

A combat round in Trenches and Alchemy exists in multiple ‘states’ that can all be taken at will by the Players and the Game Master in controlling the various characters and non-player characters under their control over the course of the game.  Movement, Actions, Reactions, and Special Actions can all be taken at any point over the course of a turn.  Each combat round consists of ‘turns’, given to the player(s) and/or NPC(s) who are involved in the fight based on initiative roles.  These rolls are a basic D20 roll with the addition of a character’s dexterity modifier.  In the event of tied rolls for turn-order, the character / NPC with the highest base roll (lower dexterity modifier) goes first.  If the base rolls are the same, the character / NPC who rolled first will go first.  At the end of all of the turns being taken by all conscious characters / NPCs, a new combat round will start if the combat has not ended.  Each combat round is 6 seconds long, and all characters / NPCs are considered to be moving in that same 6 second span of time.

The components of a combat turn for any given character are as follows:

Movement encompasses the movement of a character or NPC token around the map provided by the Game Master.  Trenches and Alchemy encourages the use of a 5m grid-system to allow for some at least somewhat accurate simulation of the distances of engagements.  While most humanoid character or NPCs are allowed 30m of movement within any single turn, there are some creatures outlined in the bestiary which might have significantly higher or lower speeds.  Movement can further be impacted by factors like difficult terrain which will halve movement speed across it, or by certain actions.  Certain states might impede movement speed, or take away from base movement speed as outlined elsewhere in the Player’s Handbook.

Actions are the most varied of the components of a turn in a combat round.  Encompassing everything from potentially clearing barbed wire with wire-cutters for others to pass through an area unimpeded to firing a weapon or using a melee weapon to applying bandages to stabilize an ally (or enemy) in combat.  The use of most equipment will describe if an action is necessary to use it, and all attacks will be defined as requiring a full action unless some other perk or ability would otherwise impact such.  The few non-equipment based actions include sprinting, grappling, shoving, or throwing yourself prone.  While grappling and throwing yourself prone are covered elsewhere in much more detail, sprinting and shoving are somewhat more unique actions.

Sprinting allows for a character to move double their usual movement speed at the cost of an action to rapidly close (or open up) the distance between themselves and enemies or dangerous situations.

Special Actions are specific actions which can be taken in particular circumstances in order to achieve a particular goal.  The most common example of this is when preparing Consumable Imbued Munitions to be used with an action.  Retrieving a grenade and pulling the pin on it to throw it, preparing and chambering a specially imbued round, or any other action which is specifically noted as a special action will consume this portion of the combat turn for the combat round.

Reactions are another special type of action which cannot actually be taken on one’s turn.  They include (but are not soley limited to) attacks of opportunity.  Reactions are simply actions which can be taken within a turn that make sense contextually and are entirely dependent upon other actions being taken by other characters / NPCs involved in the combat round.

Attacks of opportunity are attacks taken when an enemy, previously within melee distance, attempts to disengage by turning their backs and fleeing the fight.  By doing so, they expose themselves to an easy attack by whoever they might be in combat with by being adjacent to them.  Any creature within 5m of an enemy who attempts to leave the 5m radius of that creature without disengaging will take such an attack as an optional reaction.  This attack will be rolled with whatever modifiers would be appropriate as they left their immediate 5m radius.

Armor Class (AC)

Armor-class in Trenches and Alchemy are somewhat different from how such is normally calculated.  Rather than relying on the dexterity stat in conjunction with any equipment, AC is reliant entirely upon the endurance stat.  AC starts with a base of 10 and can be increased according to the endurance modifier.  AC can also be increased on the simple basis of finding particular relics, trinkets, armors, or gaining specific perks which might increase the AC of an individual through any number of other means on the battlefield.  The reason for the change away from dexterity-based AC is largely due to the incredible amount of attributes otherwise given to the stat and the huge dependence of such within combat.  AC is independent for firearms and for melee attacks, given that certain equipment might be better-suited for one type or the other of damage to be mitigated or deflected.


There are a variety of status conditions that can be imposed by a number of the conditions of the battlefield, effects of combat, and effects of the alchemical processes that are changing the nature of both of the others. Most conditions are impairments and negatively affect the combat (and skill) abilities in some way or another.

A condition lasts either until it is countered (the prone condition is countered by standing up, for example) or for a duration specified by the effect that imposed the condition.

If multiple effects impose the same condition on a creature, each instance of the condition has its own duration, but the condition’s effects don’t get worse. A creature either has a condition or doesn’t.

The following definitions specify what happens to a creature while it is subjected to a condition.


  • A blinded creature can’t see and automatically fails any ability check that requires sight.

  • Attack rolls against the creature have advantage, and the creature’s melee attack rolls have disadvantage.  Any ranged attack rolls beyond 10m are on disadvantage and have a -5 penalty as well.


  • A deafened creature can’t hear and automatically fails any ability check that requires hearing.

  • Any deafened creature oftentimes is unbalanced thanks to the damage to the inner-ear, temporary or not.  As such, a deafened creature loses ? of its move-speed for the duration that it is deafened. 


See Exhaustion (below).


  • A frightened creature has disadvantage on ability checks and attack rolls while the source of its fear is within line of sight.

  • The creature can’t willingly move closer to the source of its fear.


  • A grappled creature’s speed becomes 0, and it can’t benefit from any bonus to its speed.

  • The condition ends if the grappler is incapacitated (see the condition).

  • The condition also ends if an effect removes the grappled creature from the reach of the grappler or grappling effec.


  • An incapacitated creature can’t take actions, reactions, or special actions unless specifically denoted as being possible.


  • A paralyzed creature is incapacitated and can’t move or speak.

  • The creature automatically fails strength and dexterity saving throws.

  • Attack rolls against the creature have advantage.

  • Any attack that hits the creature is a critical hit if the attacker is within 5m of the creature.


  • A prone creature’s only movement option is to crawl, unless it stands up and thereby ends the condition.  Crawling speed is ? base movement speed, and while crawling a creature cannot make use of the ‘sprint’ action.  Choosing to stand from prone costs the creature ? of that turn’s movement speed.

  • The creature has disadvantage on attack rolls.

  • An attack roll against the creature has advantage if the attacker is within 5m of the creature. Otherwise, the attack roll has disadvantage.


  • A restrained creature’s speed becomes 0, and it can’t benefit from any bonus to its speed.

  • Attack rolls against the creature have advantage, and the creature’s attack rolls have disadvantage.

  • The creature has disadvantage on Dexterity Saving Throws.


  • A stunned creature is incapacitated (see the condition), can’t move, and can speak only falteringly.

  • The creature automatically fails Strength and Dexterity Saving Throws.

  • Attack rolls against the creature have advantage.


  • An unconscious creature is incapacitated, can’t move or speak, and is unaware of its surroundings

  • The creature drops whatever it’s holding and falls prone.

  • The creature automatically fails Strength and Dexterity Saving Throws.

  • Attack rolls against the creature have advantage.

  • Any Attack that hits the creature is a critical hit if the attacker is within 5m of the creature.


Some special abilities and environmental hazards, such as starvation and the long–term effects of freezing or scorching temperatures, can lead to a special condition called exhaustion. Exhaustion is measured in six levels. An effect can give a creature one or more levels of exhaustion, as specified in the effect’s description.

1Disadvantage on all ability checks

2Movement speed is reduced to ? 

3Disadvantage on all attack rolls and saving throws

4HP points halved

5Movement speed reduced to 0


Effects are cumulative.  Finishing a long-rest reduces a creature’s exhaustion level by 1, provided that the creature has also eaten and drank during the period of the long-rest.  All exhaustion effects are removed if the exhaustion is reduced below 1.  (To the natural ‘rested’ state of 0)


Environmental Effects

Trench warfare and the subsequent potential of exploring the origins of alchemy can involve delving into places that are dark, dangerous, and full of a number of hazards and obstacles that need to be met. The rules in this section cover some of the most important ways in which adventurers interact with the environment in such places.


A fall from a great height is a rare, but real hazard facing those who may suddenly find themselves at a precipice. At the end of a fall, a creature takes 1d6 bludgeoning damage for every 10 feet it fell, to a maximum of 20d6. The creature lands prone, unless it avoids taking damage from the fall.


A creature can hold its breath for a number of minutes equal to 1 + its Endurance modifier (minimum of 30 seconds).  A creature may choose whether or not to hold their breath when faced with the potential of breathing in some potentially toxic sort of gas they have noted (or believe that they have noted)

When a creature runs out of breath or is choking, it can survive for a number of rounds equal to its constitution modifier (minimum of 1 round). At the start of its next turn, it drops to 0 Hit Points and is dying, and it can’t regain Hit Points or be stabilized until it can breathe again if it is in an environment where it cannot breathe.  If the creature is in an environment where they can breath, they cannot force themselves to be incapacitated by simply not breathing, and after the time they can hold their breaths is up they will be forced to resume breathing for at least another minute.For example, a creature with an endurance of 14 can hold its breath for 3 minutes. If it starts suffocating, it has 2 rounds to reach air before it drops to 0 Hit Points.

Vision and Light

The most fundamental tasks of adventuring— noticing danger, finding hidden objects, hitting an enemy in combat, and targeting a spell, to name just a few—rely heavily on a character’s ability to see. Darkness and other effects that obscure vision can prove a significant hindrance. A given area might be lightly or heavily obscured. In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight. A heavily obscured area—such as darkness, opaque fog, or dense foliage—blocks vision entirely. A creature effectively suffers from the blinded condition (see conditions) when trying to see something in that area.

The presence or absence of light in an environment creates three categories of illumination: bright light, dim light, and darkness.

Bright light allows most creatures to see normally. Even gloomy days provide bright light, as do lamps, lanterns, fires, and other sources of illumination within a specific radius as is usually denoted on their item sheets or as can be determined by the GM in the case of an even more specific example being wanted.

Dim light, shadowy areas are generally lightly obscured areas. An area of dim light is usually a boundary between a source of bright light, such as a torch, and surrounding darkness. The soft light of twilight and dawn also counts as dim light. A particularly brilliant full moon might bathe the land in dim light.

Darkness creates a heavily obscured area. Characters face darkness outdoors at night (even most moonlit nights), within the confines of an unlit dungeon or a subterranean vault, or in any other areas that would be obscured by darkness.


A creature with blindsight can perceive its surroundings without relying on sight, within a specific radius. Creatures without eyes, such as oozes, and creatures with echolocation or heightened senses, such as bats, have this sense.  While rare, the few creatures with this sort of ‘sight’ are potentially very dangerous to those who rely upon their eyes instead- having distinct advantages in the dark- and potentially simply even where direct sight is otherwise impossible.


Some creatures in Trenches and Alchemy, especially those that dwell underground, have darkvision. Within a specified range, a creature with darkvision can see in darkness as if the darkness were dim light, so areas of darkness are only lightly obscured as far as that creature is concerned. However, the creature can’t discern color in darkness, only shades of gray.

Food and Water

Characters who don’t eat or drink suffer the Effects of exhaustion (see conditions). Exhaustion caused by lack of food or water can’t be removed until the character eats and drinks the full required amount.


A character needs one full set of rations per day and can make food last longer by subsisting on half rations. Eating half-rations will count as ? a day without food rather than a full day.

A character can go without food for a number of days equal to 3 + his or her endurance modifier (minimum 1). At the end of each day beyond that limit, a character automatically suffers one level of exhaustion.

A normal day of eating resets the count of days without food to zero.


A character needs four liters of water per day, or eight liters per day if the weather is hot. A character who drinks only half that much water must succeed on a DC 15 endurance saving throw or suffer one level of exhaustion at the end of the day. A character with access to even less water automatically suffers one level of exhaustion at the end of the day.

If the character already has one or more levels of exhaustion, the character takes two levels in either case.


A character in Trenches and Alchemy is reasonably able to go without sleep given the time that they have doubtless spent in the trenches- but it is also something that they’ve learned to grab whenever they can to keep themselves strong.  A character is able to go without significant sleep for 1+ ? his or her endurance modifier days (minimum 1).  At the end of each day beyond that limit, suffering one level of exhaustion. 

Significant sleep’ is qualified as being able to sleep at least 6 hours of more with only light or otherwise reasonable interruptions in their sleep.  It is the minimum necessary for a soldier to function in some reasonable capacity rather than merely as a shambling extra body on the frontlines.  Most of those in the trenches find themselves easily capable of getting this much sleep between their various shifts and duties, unless otherwise indicated or stated by the GM.

Poor sleep is qualified as being able to sleep at least a little during the times that might be significantly more stressful in some way.  Constant shelling, assaults at regular intervals that prevent anything longer than 1 hour’s rest, or any other circumstance that might be dictated as- at best, interrupted rest over the course of a day.

Interacting with Objects

A character’s interaction with objects in an environment is often simple to resolve in the game. The player tells the GM that his or her character is doing something, such as moving a lever, and the GM describes what, if anything, happens.

For example, a character might decide to interact with some object in an enemy’s cleared trench, a lever or a button after finding it and thereby open a door or trigger an intercom system into a bunker hidden within the trench.  If somehow the object was something that might require some sort of skills to operate, being damaged or otherwise needing some additional ‘extra’ push, it might require a skill-roll to operate.  According to the GM’s discretion based on the situation.

Characters can also damage objects with their weapons and certain equipment. Objects can be affected by physical attacks much like creatures can. The GM determines an object’s AC and HP, and might decide that certain objects have resistance or immunity to certain kinds of attacks. (It’s hard to cut a rope with a club, for example.) Objects always fail strength and dexterity Saving Throws, and they are immune to effects that require other saves. When an object drops to 0 HP, it breaks.

A character can also attempt a strength check to break an object. The GM sets the DC for any such check.

Game Mechanics


A familiar system in a number of tabletop games; sometimes a special ability or perk tells you that you have advantage or disadvantage on an ability check, a saving throw, or an attack roll. When that happens, you roll a second d20 when you make the roll. Use the higher of the two rolls if you have advantage, and use the lower roll if you have disadvantage. For example, if you have disadvantage and roll an 18 and a 11, you use the 11. If you instead have advantage and roll those numbers, you use the 18.

If multiple situations affect a roll and each one grants advantage or imposes disadvantage on it, you don’t roll more than one additional d20. If two favorable situations grant advantage, for example, you still roll only one additional d20.

If circumstances cause a roll to have both advantage and disadvantage, you are considered to have neither of them, and you roll one d20. This is true even if multiple circumstances impose disadvantage and only one grants advantage or vice versa. In such a situation, you have neither advantage nor disadvantage.

When you have advantage or disadvantage and something in the game, lets you reroll the d20, you can reroll only one of the dice. You choose which one. For example, if a character has advantage or disadvantage on an ability check and rolls a 1 and a 13, the character could use such a trait to reroll the 1.

You usually gain advantage or disadvantage through the use of special abilities, actions, or equipment. The GM can also decide that circumstances influence a roll in one direction or the other and grant advantage or impose disadvantage as a result

Proficiency Bonus

Characters have a proficiency bonus which is added to many of their skill-checks. Other creatures can also have this bonus, which is incorporated in their stat blocks. The bonus is used in the rules on ability checks- and may be extended in some way to attacks or saving throws later in the game.

Your proficiency bonus can’t be added to a single die roll or other number more than once. For example, if two different rules say you can add your proficiency bonus to a wisdom saving throw, you nevertheless add the bonus only once when you make the save.

Occasionally, your proficiency bonus might be multiplied or divided (doubled or halved, for example) before you apply it. If a circumstance suggests that your proficiency bonus applies more than once to the same roll, you still add it only once and multiply or divide it only once.

By the same token, if a feature or effect allows you to multiply your Proficiency Bonus when making an ability check that wouldn’t normally benefit from your proficiency bonus, you still don’t add the bonus to the check. For that check your proficiency bonus is 0, given the fact that multiplying 0 by any number is still 0. For instance, if you lack proficiency in the history skill, you gain no benefit from a feature that lets you double your proficiency bonus when you make intelligence (History) checks.

In general, you will not multiply your proficiency bonus for attack rolls or saving Throws. If a feature or effect allows you to do so, these same rules apply.

Proficiency bonuses are generally increased by surviving on the battlefield and making use of a skill for a prolonged period of time.  Therefore, proficiency bonuses increase over time and allow the character to potentially have far more capacity in whatever they are doing as time goes on.  A looter, whose investigation and stealth- their abilities to find loot worth keeping and ability to hide in the night when going through their grizzly activity- will initially start off as merely impressive to see, may well suddenly find themselves in a situation of being able to find more loot and be at less risk of even more advanced detection measures years into a campaign.

Year 1

Year 2

Year 3




Furthermore, beyond the third year, any character is able to take another proficiency on every third year to add to their proficient skills.  This is to allow for the character to undertake more of the responsibilities in the Trenches and to slowly and surely expand their skills outside of what their lives had prepared them for in the world outside of that of war.

Ability Checks

An ability check tests a creature’s general capability to overcome a particular challenge. The GM calls for an ability check when a character or monster attempts an action (other than an attack) that has a chance of failure. When the outcome is uncertain, the dice determine the results.

For every ability check, the GM decides which of the six abilities is relevant to the task at hand and the difficulty of the task, represented by a difficulty class. The more difficult a task, the higher its DC. The typical difficulty classes table shows the most common DCs.

Typical Difficulty Class

Difficulty Class (DC)

Very Easy








Very Hard


Near Impossible


To make an ability check, roll a d20 and add the relevant ability modifier. As with other d20 rolls, apply bonuses and penalties, and compare the total to the DC. If the total equals or exceeds the DC, the ability check is a success—the creature overcomes the challenge at hand. Otherwise, it’s a failure, which means the character or monster makes no progress toward the objective or makes progress combined with a setback determined by the GM.  A critical success will result in a success as to the situation- at the GM’s discretion as to how it was achieved if the check was something that the character otherwise might not have been able to achieve given the various statistical differences between the check and the character.


Sometimes one character’s or monster’s efforts are directly opposed to another’s. This can occur when both of them are trying to do the same thing and only one can succeed, such as attempting to snatch up a weapon that may have fallen to the floor in a skirmish. This situation also applies when one of them is trying to prevent the other one from accomplishing a goal— for example, when a creature tries to barge through a door that has been shut against it. In situations like these, the outcome is determined by a special form of ability check, called a contest.

Both participants in a contest make ability checks appropriate to their efforts. They apply all appropriate bonuses and penalties, but instead of comparing the total to a DC, they compare the totals of their two checks. The participant with the higher check total wins the contest. That character or creature either succeeds at the action or prevents the other one from succeeding.

If the contest results in a tie, the situation remains the same as it was before the contest. Thus, one contestant might win the contest by default. If two characters tie in a contest to snatch a fallen weapon off the ground they will keep one another entangled and both will be unable to retrieve it. In a contest between a creature trying to open a door and another character trying to keep the door closed, a tie means that the door remains shut.

Saving Throws

A saving throw—also called a save—represents an attempt to resist an alchemical effect, a trap, a poison, a disease, or a similar threat that presents itself suddenly and (usually) violently. You don’t normally decide to make a saving throw; you are forced to make one because your character or monster is at risk of harm.

To make a saving throw, roll a d20 and add the appropriate ability modifier. For example, you use your dexterity modifier for a dexterity saving throw.

A saving throw can be modified by a situational bonus or penalty and can be affected by advantage and disadvantage, as determined by the GM.

The Difficulty Class for a saving throw is determined by the effect that causes it, which is usually determined by the item(s) used that would induce such a saving throw.  Most of these are somewhat static, and in the item descriptions or consumable imbued munitions descriptions of attack effects.

The result of a successful or failed saving throw is also detailed in the effect that allows the save. Usually, a successful save means that a creature suffers no harm, or reduced harm, from an effect.


Sickness tears through a trench like few things short of artillery shells or an enemy assault.  Ripping apart any sense of order, any semblance of a defence against an enemy in any meaningful way as soldier after soldier falls ill.  A battle can be won or lost weeks before the ‘over the top’ order is called as men lie in a hole in the ground slowly feeling their lives ebbing away through open sores.

Some diseases are well understood and given time, food, water, and sufficient rest are nothing more than an inconvenience and something of a discomfort for a character, party, or the entire trench even in the case of it spreading near-uncontrollably.  Others can be more devastating than a battle that breaks the line- wiping out entire trenches and leaving only corpses that even the enemy would be hesitant to move given the fear and pain in the rictus grins of the newly-made cadavers.

A disease that does more than infect a few party members is primarily a plot device. The rules help describe the effects of the disease and how it can be cured, but the specifics of how a disease works aren’t bound by a common set of rules. Diseases can affect any creature, and a given illness might or might not pass from one race or kind of creature to another. What matters is the story you want to tell when using these as a plot-device.  Are sickly wolves a sign of the state of the world in general or merely an outbreak that has occurred in the nearby pack?  Is it possible to use your own dead to your advantage?  Ingenuity is the core of all tabletop role-playing games.

Sample Diseases

The diseases here illustrate the variety of ways disease can work in the game. Feel free to alter the saving throw DCs, incubation times, symptoms, and other characteristics of these diseases to suit your campaign.


Trench Gut

Trench gut is a rather broad term used by the men and women fighting in the trenches to describe practically any of at least two-dozen known illnesses of the stomach that can be considered to be the result of eating ‘bad rations’, though it is more often the result of unsanitary conditions combined with generally poor hygienic practices with foodstuffs.


When a humanoid creature consumes food that has been compromised by the disease, generally by eating too close to garbage pits, latrines, or even those who have recently contracted trench gut (and may merely be in the incubation period), the creature must succeed on a DC 12 endurance saving throw or become infected.

It takes 1d4+1 days for trench gut’s symptoms to manifest in an infected creature. Symptoms include fatigue, cramps, and generalized ‘gastric distress’. The infected creature suffers two level of exhaustion, and it has disadvantage on any rolls which would require movement to accomplish due to other concerns that come to mind.

At the end of each long rest, an infected creature must make a DC 12 endurance saving throw. On a failed save, the character gains one level of exhaustion. On a successful save, the character’s exhaustion level decreases by one level. If a successful saving throw reduces the infected creature’s level of exhaustion below 1, the creature recovers from the disease.  The infected may attempt to use multiple long rests in a single day to alleviate symptoms- any beyond the first of the day’s long rest failures no longer potentially adding to the creature’s exhaustion.

Considered a relatively minor threat, though a large discomfort within the trenches, those who can be officially ‘diagnosed’ with trench gut often find themselves with light-duty for at least a few days to ensure that they are not contagious but will not find themselves in more danger from the disease than is necessary.  Those with the disease are qualified as ‘fit to fight’ in a defensive capacity by most military commands, and may even be pushed into offensive roles by some of the more brutal local military commanders if it is deemed necessary to have such numbers for an assault.


In situations where keeping track of the passage of time is important, the GM determines the time a task requires. The GM might use a different time scale depending on the context of the situation at hand. In small map exploration, the adventurers’ movement happens on a scale of minutes, where they might be exploring a field-camp that they have been stationed within or some sort of a new position that was taken in a recent assault that they might want to search for valuables, intelligence, or anything else that might be worthwhile.

In a larger city, in transit, or in other situations where kilometers of distance might easily be traveled, hours are the most-common unit of measurement for shorter-distance expeditions and explorations.  Marching to a suspected wolves’ den in the heart of the woods to the east of the trenchline might well take eight hours, but given how hungry the pack has been lately…

For long journeys, a scale of days works best. Returning from the frontlines, even using a vehicle, to one of the central hubs of a nation will most likely take days, and in some cases potentially even weeks if the frontline is fortunate enough to be so far from such large centers of civilization.

In combat and other fast-paced situations, the game relies on rounds, a 6-second span of time.


In a typical tabletop campaign, characters aren’t driven mad by the horrors they face and the carnage they inflict day after day, but sometimes the stress of being a soldier in the world of Trenches and Alchemy can push them over the edge. If your campaign has a strong theme of incorporating an additional system to reflect the horrors of war, you might want to use madness as a way to reinforce that theme, emphasizing the extraordinarily horrific nature of the threats the characters of the game face.

Going Mad

Various effects can inflict madness on an otherwise stable mind. Certain horrific sights can cause insanity, and you can use the madness rules here to help demonstrate how to inflict madness upon a character. Some artifacts can also break the psyche of a character who uses or becomes attuned to them due to the incredibly strong alchemical nature of the artifacts being potentially too much for a human’s mind to necessarily fully be able to make use of.

Madness can be incurred by depletion of a sanity meter, which is 6 +Charisma Modifier +Intelligence Modifier +Wisdom Modifier (without dropping below 5 and without going above 15).  Sanity losses are determined by the GM, and similarly there are a number of activities which can be used to restore sanity in a reasonable time-period.  For many, restoration of sanity will likely involve some sort of vice.  Alcohol, gambling, or potentially even visiting various ‘recreational’ activities that may be considered to be of ‘greater or lesser taste’

Madness effects

Madness can be short-term, long-term, or indefinite. Most relatively mundane effects impose short-term madness, which lasts for just a few minutes. More horrific effects or cumulative effects can result in long-term or indefinite madness.

A character afflicted with short-term madness is subjected to an effect from the Short-Term Madness table for 1d10  minutes.  It can be caused if a character is determined to lose more than 3 points of sanity within a 10 minute period.

A character afflicted with long-term madness is subjected to an effect from the Long-Term Madness table for 2d10 × 10 hours.  It can be caused if a character loses more than ? their sanity over the course of a single day’s events.

A character afflicted with indefinite madness gains a new character flaw from the Indefinite Madness table that lasts until cured.  This can only be caused if a character loses all of their sanity.

Critical Successes and Critical Failures

Critical successes and their counterparts, critical failures have been something open to the interpretation of players for quite some time, and usually fall within a GM’s realm of decision-making when it comes to the dreaded 1 or the joyous revealing of a natural 20 whenever rolling for a standard roll of some sort.  In most cases, these rolls when ‘checking’ for some sort of skill-based roll mean that a character either succeeds or botches an attempt to do something in the most spectacular, plausible way possible.  However, in combat there is something of a caveat when in Trenches and Alchemy…

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