Combat Mechanics Primer

Class touchstones

Every player class declares a prime attribute and THAC0 progression in class_table. The prime stat feeds the new damage-cap formula while the THAC0 entries drive hit-roll interpolation.

Source: class_table definition.【F:src/const.c†L640-L659】

Attack roll flow

1. Setup: one_hit resolves the weapon type, skill, and damage type. Undefined attacks adopt the wielder’s weapon damage type or the character’s innate dam_type.【F:src/fight.c†L603-L676】
2. THAC0: NPCs pick baseline values by role flag while PCs pull thac0_00 and thac0_32 from class_table. Interpolation by level plus hitroll, skill, and backstab adjustments produces the final to-hit target.【F:src/fight.c†L695-L720】
3. Armor check: The defender’s armor entry for the damage type is divided by ten. Extreme negatives suffer diminishing returns via (ac + 15) / 5 - 15. Visibility and posture then modify the effective AC before a 0–19 d20 roll determines success.【F:src/fight.c†L722-L763】
4. Defences: On weapon hits the game checks parry, shield block, then dodge in that order. Each routine scales from either NPC level caps or the defender’s trained skill values.【F:src/fight.c†L1080-L1091】【F:src/fight.c†L1813-L1993】

Offensive scaling

• Base damage: Weapon attacks roll the weapon’s dice and multiply by skill%; fighting without a shield grants a 5% bonus. Unarmed PCs use a level-scaled range. Enhanced damage, position-based multipliers, backstab/critical bonuses, and damroll all stack before the result is handed to damage(). Off-hand swings are reduced to 60% power. 【F:src/fight.c†L769-L867】
• Damage cap: calculate_damage_cap() clamps each damage packet to 150 + 6 × prime stat using permanent attributes. Divine strikes replace the capped value with one third of the victim’s current hit points after immunity checks.【F:src/fight.c†L950-L1113】
• Multi-hit loop: multi_hit executes the primary swing, optional haste extra, second-attack (skill/2), third-attack (skill/4), and dual-wield dagger proc (skill/2) for player characters. NPCs use the same structure inside mob_hit with OFF_FAST and OFF_AREA_ATTACK modifiers.【F:src/fight.c†L404-L520】

Armor and mitigation

• Character reset: When equipment is re-evaluated, all four armor slots reset to 100, hitroll/damroll and saving throw bonuses clear, and each worn item is re-applied. APPLY_AC modifiers adjust every damage type simultaneously.【F:src/handler.c†L547-L624】
• Slot multipliers: apply_ac() scales armor values by wear location: body ×3, head/legs ×2, cloaks ×2, and most accessories ×1. Only ITEM_ARMOR pieces contribute.【F:src/handler.c†L1910-L1954】
• Dexterity bonus: GET_AC adds the defender’s dexterity defensive adjustment whenever they are awake. Hitroll and damroll macros likewise fold in strength-based bonuses.【F:src/merc.h†L2489-L2496】
• Resists and vulnerabilities: After defensive maneuvers the game applies immunity, resistance, or vulnerability adjustments in damage(), shaving or increasing the post-cap value before it is subtracted from hit points.【F:src/fight.c†L1094-L1113】

Saving throws

saves_spell() evaluates spell saves as 50 + (victim level − spell level) × 5 − 2 × saving_throw, with berserkers gaining a level/2 bonus. Immunity short-circuits the check while resistance/vulnerability shift the target by ±2. The final save chance is clamped to 5–95% before rolling number_percent().【F:src/magic.c†L203-L220】