Rules Reference

A quick reference for Mythras

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Core Resolution & Character

Core Resolution

Roll 1d100 vs. Skill %

Equal to or less than the skill = success. Greater = failure. 01–05 always succeeds; 96–00 always fails, regardless of skill value.

Critical: roll ≤ one-tenth of the skill (round fractions up). Fumble: roll of 99–00 (skills over 100% fumble only on 00).

Four outcome tiers only: Fumble / Failure / Success / Critical — there is no separate “Special” tier.

Difficulty Grades

Modify the skill before rolling.

GradeModifier
AutomaticNo roll needed
Very Easy×2 skill (or +40%)
Easy×1.5 skill (or +20%)
StandardNo change
Hard−⅓ skill (or −20%)
Formidable−½ skill (or −40%)
Herculean÷10 skill (or −80%)
HopelessNo attempt possible

Opposed & Differential Rolls

Opposed: both sides roll their skill; better success tier wins. Tied tiers → highest roll (still within success range) wins.

Differential (used for combat): margin between success tiers grants the winner 1–3 Special Effects.

vs. Critvs. Successvs. Failvs. Fumble
CritWin 1Win 2Win 3
SuccessLose 1Win 1Win 2
FailLose 2Lose 1
FumbleLose 3Lose 2

Skills over 100%: the top skill subtracts (its value −100) from everyone’s skill in the contest, including its own.

Characteristics

STR
Physical strength; feeds Damage Modifier
CON
Constitution; feeds Healing Rate, HP
SIZ
Size/mass; feeds Damage Modifier, HP, Height/Weight
DEX
Agility; feeds Action Points, Initiative
INT
Reasoning; feeds Action Points, Initiative
POW
Willpower; feeds Magic Points, Luck Points
CHA
Charisma; feeds Experience Modifier

Humans: 3d6 for STR/CON/DEX/POW/CHA; 2d6+6 for SIZ/INT.

Damage Modifier

By STR + SIZ

STR + SIZModifier
5 or less−1d8
6–10−1d6
11–15−1d4
16–20−1d2
21–25+0
26–30+1d2
31–35+1d4
36–40+1d6
41–45+1d8
46–50+1d10
51–60+1d12
61–70+2d6

Each +10 after that continues the progression.

Other Derived Attributes

Action Points
INT+DEX: ≤12 = 1, 13–24 = 2, 25–36 = 3, +1 per further 12
Experience Mod.
CHA: ≤6 = −1, 7–12 = 0, 13–18 = +1, +1 per further 6
Healing Rate
CON: ≤6 = 1, 7–12 = 2, 13–18 = 3, +1 per further 6
Luck Points
POW: ≤6 = 1, 7–12 = 2, 13–18 = 3, +1 per further 6
Magic Points
= POW
Initiative Bonus
Average of DEX and INT

Skills & Passions

Standard Skills

Base % formula

SkillBase %
AthleticsSTR+DEX
BoatingSTR+CON
BrawnSTR+SIZ
ConcealDEX+POW
CustomsINT×2
DanceDEX+CHA
DeceitINT+CHA
DriveDEX+POW
EnduranceCON×2
EvadeDEX×2
First AidINT+DEX
InfluenceCHA×2
InsightINT+POW
LocaleINT×2
Native TongueINT+CHA
PerceptionINT+POW
RideDEX+POW
SingCHA+POW
StealthDEX+INT
SwimSTR+CON
UnarmedSTR+DEX
WillpowerPOW×2
Combat Style(s)STR+DEX

Professional Skills

Culture/career-dependent

SkillBase %
ActingCHA×2
AcrobaticsSTR+DEX
ArtPOW+CHA
Binding *POW+CHA
BureaucracyINT×2
CommerceINT+CHA
CourtesyINT+CHA
CraftDEX+INT
Culture (other)INT×2
Devotion *POW+CHA
DisguiseINT+CHA
EngineeringINT×2
Exhort *INT+CHA
Folk Magic *POW+CHA
GamblingINT+POW
HealingINT+POW
Invocation *INT×2
Language (other)INT+CHA
LiteracyINT×2
LockpickingDEX×2
Lore (specific)INT×2
MechanismsDEX+INT
Meditation *INT+CON
MusicianshipDEX+CHA
Mysticism *POW+CON
NavigationINT+POW
OratoryPOW+CHA
SeamanshipINT+CON
SeductionINT+CHA
Shaping *INT+POW
SleightDEX+CHA
StreetwisePOW+CHA
SurvivalCON+POW
TeachINT+CHA
TrackINT+CON
Trance *POW+CON

* Magic skill pairs by discipline: Animism = Binding & Trance; Mysticism = Meditation & Mysticism; Theism = Devotion & Exhort; Sorcery = Invocation & Shaping.

Passions

Starting %

PassionStarting %
Person (romantic/familial)30 + loved one’s POW+CHA
Person (platonic loyalty)30 + own POW, subject’s CHA
Person (aversion)30 + own POW, subject’s CHA
Organisation/group30 + own POW+INT
Race or species30 + own POW×2
Place30 + own POW+INT
Object/substance30 + own POW×2
Concept/ideal30 + own POW+INT

Rolled like a skill (1d100 vs. Passion %) to invoke heroic/reckless surges of will in relevant moments.

Hit Points by Location

CON+SIZ, humanoid

Location1–1011–2021–30
Leg (each)1–23–45–6
Abdomen2–34–56–7
Chest3–45–67–8
Arm (each)12–34–5
Head1–23–45–6

Ranges scale by CON+SIZ in bands of 5; each location gains +1 HP per further 5 points.

Combat

Initiative & Round Structure

Initiative = 1d10 + Initiative Bonus

Highest acts first, descending; ties act concurrently.

Initiative penalty: total armour ENC ÷ 5, rounded up.

Surprise: −10 to initiative, flat-footed until your turn, and the first hit against you gains a bonus Special Effect.

Round = 5 seconds. Cycle = one pass through initiative order. Each character acts as many times per round as their Action Points.

Actions

Default cost: 1 Action Point per action.

Proactive
Attack, Cast Magic, Move, Ready Weapon, Change Range, Mount, Outmanoeuvre — only on your own turn
Reactive
Parry, Evade, Counter Spell, Interrupt, Ward Location — usable anytime you have AP
Free
Assess Situation, Drop Weapon, Signal — no AP cost

Attack vs. Defense — Sequence

1. Attacker spends 1 AP, rolls Combat Style.

2. Defender may spend 1 AP to Parry/Evade, rolling their skill.

3. Compare as a Differential Roll — the better tier wins the margin.

4. The margin grants the winner 1–3 Special Effects (chosen freely, may stack where noted) — independent of whether damage lands.

5. If the attacker succeeded or critted, roll weapon damage + Damage Modifier; determine Hit Location.

6. If the defender succeeded or critted (parried), reduce damage per weapon Size comparison.

No parry available (no AP, or declined) = automatic failure, granting the attacker’s Special Effects outright.

Parry Damage Reduction

By weapon Size

Parrying weapon vs. attacker’sResult
Equal or biggerAll damage stopped
1 size smallerHalf damage stopped
2+ sizes smallerNo damage stopped

Sizes run Small < Medium < Large < Huge < Enormous.

Special Effects

Selected examples

EffectRequires
Bypass ArmourAttacker crits; stackable
Maximise DamageAttacker crits; stackable
BleedCutting weapons
Bash / Stun LocationBludgeoning
ImpaleImpaling weapons
SunderAxes, 2H weapons
Disarm OpponentOffensive or defensive
Trip OpponentOffensive or defensive
Choose LocationPick the hit location
Circumvent ParryAttacker crits
Force FailureOpponent fumbles
EntangleEntangling weapons

The full list runs to roughly 40 named effects covering offense, defense, and ranged-specific options.

Hit Location

1d20, humanoid

RollLocation
1–3Right Leg
4–6Left Leg
7–9Abdomen
10–12Chest
13–15Right Arm
16–18Left Arm
19–20Head

Mounted attacker vs. a lower target: roll 1d10+10 instead, favouring upper locations.

Damage Resolution & Wounds

Order: Damage Modifier → magic adjustments → parry reduction (by Size) → subtract Armour Points at that location.

Minor Wound
Location HP still positive — a scratch, no real effect
Serious Wound
Location HP ≤ 0 — stunned 1d3 turns; failed Endurance vs. the attack roll cripples the limb or (torso/head) knocks unconscious
Major Wound
Location HP negative by its own starting max — incapacitated, prone; failed Endurance = unconsciousness (limb) or instant death (torso/head)

Charging & Knockback

Charging: needs a full round of movement first; the attack is one grade harder; Damage Modifier improves one step (two for quadrupeds); weapon Size effectively +1.

Knockback: triggers when raw damage (pre-parry/armour) exceeds the target’s SIZ; the target rolls Easy Acrobatics or Standard Athletics or falls prone, pushed back 1m per 5 points over SIZ.

Magic

Casting Basics

Requires: clear thought, a free hand for gesture, the ability to vocalise, and (usually) sight of the target — losing any of these makes casting harder or impossible.

While casting: walking pace only, no Attack action, only Free/Reactive actions permitted.

Minor Wound while casting
Willpower check or the spell is one grade harder
Serious Wound
Willpower check: pass = one grade harder, fail = two
Major Wound
Casting automatically fails
Mental domination
Casting automatically fails

Magnitude vs. Intensity

Magnitude: how hard the effect is to dispel. Intensity: the effect’s raw power (e.g. Sorcery Intensity = one-tenth of Invocation skill). Neither changes with the casting roll’s Difficulty Grade.

Magic from different disciplines never stacks; same-discipline effects with similar purpose don’t stack either — the higher Intensity (or newer, on a tie) prevails.

Magic Points Economy

Base attribute: MP = POW. Spending fuels spells, miracles, and talents at a per-ability cost.

Self (default)
Own MP, recovers with rest
Sacrifice
Creature’s POW (or 1d3/1d6/2d6/3d6+ by size)
Magical location/object
25/50/75/100% of MP attribute, per its Magical Strength
Veneration
25% (<100 worshippers) up to 100% (10,000+)

Only the single best available source counts per recovery period — sources don’t stack. Recovery is paced 1 MP/hour to 1 MP/week depending on setting. Running out (default): you simply can’t cast further, no extra penalty.

Learning New Abilities

DisciplineAbilityXP RollsTime
Folk MagicCantrip/Charm31 week
AnimismSpirit51 month
MysticismTalent51 month
SorcerySpell51 month
TheismMiracle51 month

A beginning magician knows 1 ability per full 20% (or part) of their governing magic skill.

The Five Magical Disciplines

Folk Magic (Folk Magic, POW+CHA)
Simple community-taught cantrips, limited effects, open to almost anyone; content varies by culture.
Animism (Binding & Trance)
Builds relationships with spirits bound to the mortal world to work magic; teaches restraint and reciprocation with nature.
Mysticism (Meditation & Mysticism)
Inner contemplation and philosophical insight channel power from within the self, not an external source.
Sorcery (Invocation & Shaping)
Manipulates the mathematical and existential “laws” underlying reality directly; needs no gods or spirits, flexible but viewed with suspicion.
Theism (Devotion & Exhort)
Miracles drawn from a worshipped deity via devotion; power scales with the strength of that relationship and matches the god’s portfolio.

Quick Reminders

01–05 always succeeds, 96–00 always fails, no matter the skill.

Special Effects resolve independently of damage — you can win effects and still get hit, or vice versa.

Armour reduces damage before Hit Points are touched; 0 AP means that armour location is useless.

A Combat Style is rolled like any Standard Skill (base STR+DEX) for both attack and parry.

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Based on Mythras Imperative, published by The Design Mechanism, Copyright 2023. Licensed under the ORC License. Mythras and all associated trademarks are the property of their respective owners. Full notice & attribution