The full difficulty formula

Fixed and assigned exceptions#

Rift creatures use their assigned rating. Public expedition creatures use an assigned rating clamped to D2–95. Vendors and other listed service categories rate D1; an invulnerable noncombat creature also rates D1. Champion descendants, the Harrower and the Dark Father rate D100. Instant-kill guards also rate D100 when that rule is enabled.

Other creatures use the formula below, rounded with the runtime’s normal nearest-even rounding and clamped to 1–99. A wild, nonsummoned greater dragon has a minimum of D80, or D95 if paragon. Difficulty is not defined for players.

Health and durability#

Average resistance R is the arithmetic mean of physical, fire, cold, poison and energy resistance. Clamp R to 0–85 for the health calculation. Effective health H = max(1, maximum hits) / (1 − R / 100).

Reference kill time T = H / 25. Durability score = 24 × log10(1 + T / 3.2). The 25 damage-per-second reference is a provisional calibration constant, not a prediction of how quickly every build will kill that creature.

Melee pressure#

C is the highest base skill among Wrestling, Swordsmanship, Fencing, Mace Fighting and Archery. A is max(1, the mean of minimum and maximum base damage).

Melee pressure M = A × (0.5 + clamp(C, 0, 150) / 200) × (0.6 + max(0, Tactics) / 150 + max(0, raw Strength) / 500) × (0.75 + clamp(raw Dexterity, 0, 300) / 300). Offense score = 12 × log10(1 + M / 10).

The damage range comes first from a creature’s configured DamageMin/Max. Otherwise it comes from an equipped one- or two-handed weapon. A nonhuman creature without that range uses max(1, raw Strength / 28); the remaining fallback is 1–4 damage.

Casting and resistance skill#

Only mage AI receives the casting component. Casting = min(18, Magery / 15 + Evaluating Intelligence / 40 + Necromancy / 40 + log10(1 + max(0, raw Intelligence) / 100)). A melee-only creature does not receive this bonus merely for having magic skills.

Magic-resistance score = clamp(base Resisting Spells / 50, 0, 3). Before exceptions, rating = round(1 + durability + offense + casting + magic-resistance score + ability score).

Ability score#

Add the applicable components below, then cap the total ability score at 18. A weapon-ability override contributes even when that override chooses its ability randomly. For a MonsterAbilityGroup, the strongest contained ability contributes instead of summing every group member.

Why one creature type can have several ratings#

The calculation reads current maximum health, resistances, raw stats, base skills and active AI. Random stat rolls, alternate constructors, paragon conversion and scripted forms can change those inputs. The catalogue therefore keeps fixed ratings, baseline estimates and unresolved formulas distinct.