Combat Core Rules

The finished homebrew d20 engine every class and every House runs on. Built from the Mage System reference, with the character-wide pieces the Mage doc left open (HP, ability scores, skills, conditions, rest) filled in. Companion to the Design Overview, which holds the roster, the Houses, the HUD layout, and the architecture. Every number here is tunable; mark anything you want changed.

If you have an older core or character-creation doc, send it and it overrides the proposed values below.

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1. Levels and progression

Characters run levels 1 to 10. Each class names its own title bands (the Mage uses Apprentice, Initiate, Adept, Scholar, Master, Archmage). The mechanical spine is the level modifier, shared by all classes:

Action mod adds to everything you do (cast, strike, maneuver). Resist mod adds to every save you roll. This is the homebrew's proficiency bonus.

2. Ability scores (the Stats button)

Six scores, rated 1 to 5. Modifier = score minus 3 (so 1 is -2, 3 is 0, 5 is +2). Average is 3. Modifiers stay small on purpose so level remains the main driver, which keeps the Mage doc's DCs valid.

Starting spread (tunable): one 5, two 4s, two 3s, one 2. The familiar six names are used so House perks that say Con, Wis, Cha, or Int translate with no math. Rename freely, it is only data.

3. The four Saves (the Saves button)

Each save = 1d20 + level resist mod + the stat below. An action names which save its target rolls.

4. Action resolution (one schema for everything)

Every action a character can take, a spell, a weapon strike, a maneuver, a House power, is one data row with the same fields the Mage doc already uses:

name | unlock level | cost | Cast DC | Resist DC | resist type | damage | effects | description

Resolution: 1. Action roll. Roll 1d20 + level action mod + key stat. Meet or beat the Cast DC. On a miss the action fails and the cost is still spent. 2. Resist roll. If it lands on a target, the target rolls the named save vs the Resist DC. 3. Outcome. Resist beats the DC: negated. Resist fails: full damage and effect. Partial: fail the resist by 3 or less, half damage and reduced effect. 4. Crit hit (natural 20 on the action roll): damage dice doubled, target resists at disadvantage. 5. Misfire (natural 1 on the action roll): action lost, cost spent, minor backlash. 6. Non-combat actions: Cast DC reduced by 3; describing your approach can earn a further bonus.

Weapon strikes are just rows: a basic strike has a low Cast DC (easy to swing), the target resists with Reflex, damage is the weapon's dice. Martial maneuvers (Fury powers, trick shots) are rows with a cost. The engine never distinguishes a sword from a spell; it runs rows. That is what keeps it one brain.

Advantage and disadvantage: roll 2d20, keep the higher (advantage) or lower (disadvantage). House perks grant these often.

Situational modifiers (from the Mage doc): near a leyline +2 action; in Azura +3 action and +1 damage die; at 10% resource -2 action; at 0 resource (overdraw) -4 action and +3 to your Cast DCs; target is higher level +2 to their resist; target is non-magical -2 to their resist vs magic; target unaware -3 to their resist; attacker injured or distracted -2 action; same action used 3+ times in a scene -1 cumulative.

4.1 Power models and environmental gating

Classes share the resolution above but differ in where their abilities come from. The models so far:

• Arcane (Wizard, Azura). Abilities are learned from a list and can be re-picked on rest, like a spellbook. Fed by leylines. They create effects from nothing. The Mage System doc is the reference.
• Blooded Sorcery (Sea Shepherd, Darkcliff). Abilities are innate and fixed, never re-picked. They shape forces that already exist rather than creating them, so each one carries an environmental requirement. Power scales with proximity to the source (the sea). See the Sea Shepherd page.
• Martial Discipline (Cavalier). Trained maneuvers, no environmental gating, re-trainable on a long rest. Fueled by Conviction, a pool that also builds through valor in combat. See the Cavalier page.
• Sanctified (Paladin prestige). A narrow set of divine effects granted by a sworn oath, revocable if the oath breaks. Layers on top of a base class rather than standing alone.

Three engine features support these and any later model (the Druid's communion with nature will reuse them):

• Environmental requirement on a row: when the required force is absent (no water, no storm), the ability is unavailable and greys out. It is not a failed roll and costs nothing. Fail silent.
• Proximity modifier: a per-class value the HUD reads from the environment (for the Sea Shepherd, water proximity from llWater) that scales the action roll and the resource pool.
• Loadout flag (fixed or swappable) and magic-item attunement flag (not every class may use magic items), set per class.

5. Health (HP)

Damage is rolled in dice, so HP is a pool. Max HP = the tier value for your level plus your Constitution modifier.

Light: Wizard. Medium: Druid, Sea Shepherd, Artificer, Bard, Ranger. Heavy: Cavalier/Knight, Barbarian, Dragonrider, Fighter. At 0 HP a character is incapacitated (downed, not dead unless the scene says so) and the HUD locks them out until healed or rested.

6. Resource pool (renamed per class)

The Mage's spell points, generalized. Every class has a pool that scales with level and is spent on costed actions. Each class renames it: Spell Points, Conviction, Wild, Tide, Focus, Pressure, Verse, Fury, Ember.

Leyline and Azura columns are the casters' arcane bonus; martial pools use the base column.

Costs: at-will tricks free; tier-1 actions 1; tier-2 actions 2 to 3; tier-3 and specialization 3 to 4; capstones 6 to 8.

Recovery: long rest restores full pool and full HP; short rest (about 30 minutes of RP) restores 25% and recharges abilities marked 1/short rest; casters near a leyline may tap once per scene for 4 to 8 points.

Exhaustion (from the Mage doc): at 25% remaining, minor strain (cosmetic RP); at 10%, actions may flicker and you take -2 to action rolls; at 0, collapse, no costed actions until you recover to 25%, at-will tricks still work. Forcing an action past 0 (overdraw) draws on HP and is staff-gated.

7. Skills (the Skills button)

Non-combat checks: 1d20 + skill rank (0 to 5) + relevant stat vs a task DC.

Skill list (covers everything the House doc references): Perception, Stealth, Athletics, Acrobatics, Lore, Arcana, History, Religion, Nature, Survival, Tracking, Medicine, Persuasion, Insight, Performance, Animal Handling, Sailing and Navigation, Craft (smithing, tinkering, invention). House perks grant advantage or a flat bonus on named skills; those attach to the check.

8. Conditions

Each lasts a duration in rounds set by the action that applies it. The HUD tracks and ticks them.

9. Rest economy

Long rest: a full night or equivalent, restores HP and pool fully. Short rest: about 30 minutes of quiet RP, restores 25% of the pool and recharges 1/short-rest abilities. Leyline tap: casters near a leyline, once per scene. House perks plug straight in, since the doc's "once per long rest" and "1/short rest" lines already live here.

10. Translating House perks into this engine

The House doc is written in 5e. The conversion rules, nothing lost:

• "Advantage on X checks" stays as advantage on the matching skill (section 7).
• "Str/Dex/Con/Int/Wis/Cha save" maps to the homebrew save: Str and Con to Fortitude, Dex to Reflex, Wis and Cha to Will, Int to Arcane.
• "DC = 8 + Proficiency + Cha/Int" becomes Resist DC = 12 + level resist mod + the caster's key stat (12 is the homebrew base; tune to the tier).
• "+1 AC" becomes +1 to your resist rolls against incoming attacks.
• "Once per long rest" and "1/short rest" keep their meaning under section 9.
• "Resistance to a damage type" becomes incoming damage of that type halved for the duration.
• "Proficiency with tools or a vehicle" becomes a flat +2 or advantage on the matching Craft, Sailing, or Animal Handling check.

Each converted perk becomes one data row keyed to house, clan, and unlock level, exactly like a class ability.

11. Companions and mounts

Class mounts (the Cavalier/Knight's gryphon, the Dragonrider's earned dragon) and House or clan companions (Drakoria hippogriff, Skjaldor Skybreaker giant eagle, Skjaldor Frostwolf frost wolf, Thaloria griffon, Azura house-elf familiar, Valoria mechanical horse or flying machine) all use one companion model: own HP at the Light tier, fights on the owner's turn as a Beast Master companion, matures and gains flight at level 10 where flight applies, and can die permanently. The full panel design is in the plan doc.