Game Mechanics


Parts of this system were inspired by the one used in Origins RP (which is derived largely from the Far Recon and Tamlin House roleplays), D&D 5th Edition, FATE Core, and various other homebrew RP systems. The majority of the system was created by Cocoa, with input and playtesting from others.

If you want to use this system for inspiration, or even copy it wholesale for private games, be my guest. - Cocoa

Dice System

BrassCore by-and-large uses fudge dice, or "df" for basic skill checks. When performing a task, you will be asked to roll four fudge dice and add your skill modifier to the roll. Each fudge die either adds one, subtracts one, or does nothing to your roll.

Bob wants to attack a mutant with his combat knife. Because of his points in strength and having trained Melee, he has a base roll of 5 for this attack, and because the dagger is a Light weapon, he gets another +2 to his attack roll.
He rolls 4df+7 and gets these results:
8 (4df+7=0, 0, +, 0)
One die is positive and none are negative, giving a result of 7+1=8.
If the mutant's defense roll was at or under 8, then the attack hits.

When if an active roll ties with the difficulty check or defensive roll, treat the active roll as succeeding.


Damage and Health

All player characters begin play with at least ten points of Physical Health (PHP) and Mental Health (MHP). PHP measures how much physical damage a character can take before fainting or dying, and MHP measures how much mental damage they can take before going catatonic or insane.

Physical health is 10+resilience.
Mental health is 10+determination.

Damage is calculated based on the type of weapon used, if the attack hits:

Heavy weapons: Cannot be used to attack in the first round of a fight, and deal 1d10 damage.
Normal weapons: Does 1d6 damage.
Light weapons: Has a +2 bonus to attack rolls, and does 1d4 damage.

Explosives: Explosives are a special case, and use a variant of exploding dice (yes haha very funny) and the engineering skill. This means that you can reroll as long as you keep getting positive dice. For example, let's say Bob has a 2 in engineering, and is trying to set explosives (and does well enough that he doesn't blow up in the process). The following rolls might result.

Bob: 4df+2
Dice: 5 (4df+4=0, +, +, +)
Bob: 3df+2
Dice: 2 (3df+4=+, 0, -)
Bob: 1df+2
Dice: 2 (1df+4=0)

With a grand total of 5 + 2 +2 = 9 damage being done. Note how the number of fudge dice rolled in each iteration depends on the number of dice that came up as "+" in the previous iteration. Also not that while this is quite a bit of damage, especially for a non-combat skill, that explosives are harder to hide (usually) than guns or knives, are more likely to injure the user or fail spectacularly, and might take a turn or two to set up. Also, this damage represents the direct source of the explosion, and might be reduced as the person or object gets further away.

Sneak Attacks: Another way to modify damage is to attack a target that isn't expecting it. This can be used to represent surprise attacks or sniper shots. In order to initiate an sneak attack, two of three conditions must be met. First, is that you and your allies must not be detected by any hostiles in a scene. Secondly, you have to have some consistent environmental advantage that would still allow you to see your target but make it impossible for your target to see you. Thirdly, you must succeed a Sneak roll against the target's Perception roll on your turn before the turn you use to make the attack (alternatively, the GM can just be lenient and say you aren't seen if the circumstances are right). If you meet two of these three conditions, you can automatically fill in damage equal to your base attack roll (Stat+Skill+Specialties, does not account for other bonuses like those from Light weapons) to your damage die, then roll a smaller die to fill in the rest. The damage done with a sneak attack can still not exceed the maximum that could have been rolled with a weapon, so an assassin with 5 ranks of Melee could still only do 4 damage with a Light knife.

Bob is sneaking up on a thug in a dark alleyway, wielding his aluminum bat which is a Normal weapon. First he rolls his Sneak against the thug's Perception. It cycles back around to Bob's turn a bit later, and Bob rolls his 4df+3 Melee against the thug's Resilience and the attack hits. Since Normal weapons have a 1d6 damage die, and Bob has 3 ranks in Melee, he rolls 1d3+3 for his damage.

If you do not have access to special dice or a dicebot that can model unusual dice, just reroll the damage die until the result is either greater than the character's ranks in their attack skill or is the maximum damage on the die.

Countering Attacks:
When a character is targeted by an attack, that character's player generally has the choice of whether they want to defend with either Resilience or Acrobatics (but not both at once). If they roll greater than the attack roll, the attack misses or is blocked. In some cases, the GM might rule that you have to use one of those two rolls to counter an attack. For example, you might be able to take evasive maneuvers to try to avoid a tank shell, but no human could realistically survive a direct hit from one with no damage. Mental attacks are rarer, and are countered by Antipsychic.

Falling Unconscious:
If a character loses six PHP from one attack or four points of MHP, they fall unconscious until they receive proper treatment. Loss of mental health might also result in your character temporarily being out of your control.

Zero Health:
If a character has zero physical health, they die or are rendered seriously injured and unconscious by GM decision. If they have zero mental health then they are dead, rendered catatonic, insane, or mind controlled depending on context and by GM decision. Even if hitting 0 HP does not kill a character, it should have serious and lasting effects.

PHP and MHP are both restored by two points per in-game day, one of each at noon and midnight. In most games, any character with four or less PHP or MHP is confined to bedrest or an infirmary until they have recovered to five or more PHP and MHP. Additionally, any character who has more than five PHP and MHP but has suffered a devastating injury may be required to rest until healed, according to GM discretion. Characters who aren't in the infirmary but are under eight health in either category are advised to restrict themselves to lighter activities.

A Note About Medical:
Medical is rolled for medical knowledge up to the high-school or amateur, along with first aid. With GM approval, Medical can be rolled in place of Science in relevant situations. Also used for stabilizing wounds.

Beyond being useful as a knowledge roll, Medical can also be used to restore a character's hit points. Each character with ranks in Medical has a healing pool of Xd4 dice per run, where X is their base rank in Medical. A medic can use their turn to tend to the wounds of themself or another character, expending one of these dice and restoring hit points equal to the number rolled. Once the pool is out of dice, the character is out of healing.


Bob is at 10 PHP and takes 3 damage, going down to 7 PHP
Alice has 4d4 medical dice left in her pool
Alice heals John, rolling one of her medical die and getting an 2
Bob is now at 9 PHP
Alice now has 3d4 medical dice left in her pool

Minor injuries which do not deal real damage, as well as conditions such as bleeding, can be healed or made more stable by a medical roll against a DC set by the GM.

Initiative Order:
Initiative is determined based on character stats. The order in which characters can act once formal combat has begun goes in order of highest Speed rank to lowest Speed rank. If two characters have the same Speed rank, determine their order in the same fashion based on their Intelligence ranks. If two or more characters have the same Speed and Intelligence ranks, decide the order by a coin flip, rock-paper-scissors, or drawing names out of a hat. If new characters are introduced to combat, you will normally add them to the end of the combat cycle, barring exceptional circumstances.



  • Athletics (Pushing, pulling, gripping, trying to escape grabs)
  • Melee (Attacking someone physically at close range)
  • Ranged (heavy) (Used to wield and shoot Heavy ranged weapons)


  • Resilience (Determines physical health, can be used to try to resist attacks and other sources of physical damage)
  • Determination (Determines mental health, can be used to power through debilitating effects or when the GM needs to test willpower)
  • Antipsychic (Used to resist psychic illusions, attacks, and in some cases mind control)


  • Acrobatics (Determines maneuverability and flexibility)
  • Stealth (Used to try to go unnoticed, contested by Perception)
  • Ranged (Used to shoot Light and Normal ranged weapons)


  • Persuasion (Convincing people of you point of view, seduction, debate)
  • Bluff (Telling lies or being deceptive)
  • Intimidation (Frightening opponents)


  • Perception (The ability to observe the world around you)
  • Insight (Gaining insight into another creature's motives, truthfulness, or emotional state)
  • Logic (Puzzle-solving and investigative ability)


  • Science (Study of chemistry, mathematics, physics, biology, computer science, and other science fields)
  • Engineering (Study, invention, and repair of mechanical devices)
  • History (Knowledge of history and culture)
  • Survival (Knowledge of nature, tracking, and the wilderness)
  • Medicine (Medical knowledge and healing ability)

Characters have 15 points to spend upon character creation. It costs one point to buy a rank in a stat, or to gain expertise in a skill.
Characters can have up to 3 ranks in a stat. They can also be experts in as many skills as they want.
A character's total rank in a skill is determined by taking the ranks they have in that skill's parent stat, and adding three if they have expertise in that skill.

Specialty Skills

Some things are just not doable without training, years of experience, or a particular interest/knack for it. A skilled poet is not necessarily a skilled historian, even when both use Academics. You can't fix a nuclear reactor without a lot of training. You can't swordfight effectively just by being strong. This is where specialty skills come in: they represent the aspects of your character's background that make them unique.

There are two main types of specialty skills (there's really a lot more because people are unbelievably creative, but we'll focus on these two for now). The first is a specialty that provides a bonus to a certain action in certain conditions. This could, for example, be a bonus to shooting with a heavy weapon against a certain kind of target, or a bonus to knowledge rolls about reptiles (note that this could apply to either Science or Medicine rolls about reptiles, but because it's so situational you don't have to limit it to just one skill). The second, slightly rarer specialty skill is rolled on its own rather than boosting other rolls. This is usually done to accommodate for a certain skill that you think fits your character both thematically and mechanically, but for one reason or another was not covered in the main stats and skills. These talents are usually niche abilities, but can be incredibly useful utilities in the right hands. It's also worth noting that certain actions (such as repairing a nuclear reactor) can only be attempted by characters with ranks in the appropriate specialty skill, but that said specialty could be either of the two types above. It's advised that you work with the GM running your game and even other players to come up with specialty skills that will be useful and fun for your character without overshadowing other characters or derailing the plot.

For more information about building specialties and their role in Horizons, please read Horizons 101.

You get 8 points to spend in specialty skills of your choosing. The upper limit for spec ranks is 4 per spec. Be sure to describe the sorts of skills that each specialty encompasses, and your character's history should show how your character learned to do that.

On the whole, characters should probably not have base rolls of above 10 (the result of a rank 4 boosting specialty applying to a maximum ranked skill, and even then this should be rare) or below 0 barring truly exceptional circumstances.
Feel free to have some fun with your specialty skills, but don't go overboard.

Character Advancement

Character advancement takes place in four different ways: Improvements, Loot, Contacts, and Training.

  • Improvement is the rarest, but also most reliable form of advancement. At the end of a story arc at your table, each character whose player has contributed to the story and been active in character interactions gets a single extra point to spend on stats and skills. While this rate of growth may seem slow compared to other game systems, it exists to ensure veteran characters will not continually overshadow the new meat.
  • Loot is awarded by the GM on a case-by-case basis. Loot might provide a slight mechanical bonus in certain situations like an equipable specialty skill, have no mechanical effect but still be useful in other ways, or simply provide a bit of neat flavor for your character. It can also be awarded as a result of your party capturing a powerful object in-game.
  • Contacts represent the alliances that your character forms as they travel and act through the world of the RP. Contacts almost never join the party proper, but can be called upon as a source of information, favors, or pulling strings behind the scenes to make a story obstacle easier to overcome. You can also lose a contact by mistreating them or relying on them too much.
  • Training represents a more limited, but also more flavorful version of specialty skills that characters can pick up over the course of the game. There are two kinds of training. The first provides a limited number of situational bonuses. For example, training in marksmanship might give you three uses of a +2 bonus to ranged that you hold onto until you use them. The second kind is a permanent trick picked up by your character. For example, your adventurer might learn how to fly a plane, your party face how to captivate audiences with a song, your magic swordsman might learn a long-forgotten fighting style that gives him an edge in certain situations. Rather than a mechanical boost, these skills are a storytelling device above all else. In order to train a skill, a character must find an NPC with that skill (or more rarely, a book), and spend a GM-determined amount of time practicing it.

Optional Rules

Gifted Characters

Gifts, magic, anomalies, superpowers. Whatever you call then, superhuman powers can add a certain dramatic flair to almost any setting. This is an optional rule that you elect to include in your campaign. Mechanically, all gifts must be listed as Specialty skills.

Since power has a price, any gifted character whose gift has more than two ranks gains a gifted flaw - some consequence of their nature that is a detriment to the character. It must limit them in some way when they're NOT trying to utilize their gifts - not being able to use one's abilities in the dark is not an adequate flaw.

Water-weaver 3. Alice is a talented aquamancer; she has the ability to control and manifest water. As a consequence of this, Hanna requires a very high intake of water, up to three times as much as a normal human. This requirement is higher in high-usage situations. She's also more vulnerable than others to taking damage from thirst in hot, arid climates as a result.

Character Death Variants

Alternative to the core zero health mechanics, you can have a character that's at 0 HP hang in the balance between life and death. Upon reaching 0 HP, the character falls unconscious and gains a 'death clock,' which starts with a value of 0. Whenever a character starts their turn at 0 HP, roll 1d20-11 and add the result to the death clock. When a character takes damage (mental if at 0 MHP, physical if at 0 PHP) while unconscious, subtract the result from their death clock (and unconscious characters are treated as automatically failing all defense rolls). If the death clock ever falls below -10, the character dies. If the character's death clock is at or above 10 when they start their turn, they are still unconscious and at 0 HP, but do not have to roll for their death clock. If the character rolls a natural twenty when rolling for their death clock, they regain consciousness with 1 HP. When a character rises above 0 HP, their death clock disappears.
On the start of your fourth turn after gaining a death clock, check the death clock value. If it is at or above zero, they stabilize at 0 HP. If they are negative, they die.

For the most part, Horizons will use the death clock system, exceptions being when a player requests not to or a GM rules there's really no way they could survive something (e.g., you just had an aircraft carrier dropped on you).

Another variant that you can use when it comes to character death is the introduction of a resurrection mechanic. Often, this involves the intercession of a powerful Gifted character, but can also take the form of other powerful plot devices, loot, or even a particularly powerful contact. You may even choose to reflect a character returning to life in a manner outside of normal mechanics, to represent the miraculous scale of it. In any case, try to keep resurrections few and far between. A character coming back from the dead should not be a run-of-the-mill event.

For Horizons, resurrection rules are being included in the mechanics page on the very small off-chance they are ever used, but there are currently no plans to use them so please do not plan on or expect them.

Uncertain Initiative

In some cases, your group may want to mix up the order of initiative, rather than just letting the characters with the highest Speed and Intelligence always go first. This is easily done. Just have each player roll a single fudge die (and have the GM roll for each enemy character) and add the result to the values used to calculate that character's initiative.

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