Affect types, resistances and vulnerabilities

Every weapon, skill, or spell has a specific affect type. Items, skills, or racial traits can grant vulnerability, resistance, or even immunity to certain affect types.

HOW IT WORKS

• Vulnerability vuln: hits of this affect type deal noticeably more damage, and spells (magic or prayers) land more often.
• Resistance resist: hits of this affect type deal noticeably less damage, and spells land less often.
• Immunity immune: hits of this affect type deal no damage at all, and spells fail completely. Immunities are very rare.
• They do not stack: two resistances to the same hit are no better than one. Vulnerability and resistance together cancel out -- the damage is normal. Immunity beats both.
• Resistance to weapons works against every weapon hit, whatever its damage type: bash, pierce, slash or, say, poison. The damage type is checked in the same go, so a weapon resist plus a poison resist on one hit still count as one resistance.
• The weapon's material is checked on its own, apart from the damage type. Vulnerability to iron against an iron sword and a weapon resist cancel each other out, and the hit lands at normal damage.
• Resistance to spells covers both magic and prayers. Resistance to magic covers only magic, resistance to prayers only prayers.

AFFECT TYPES

• Weapon: most physical effects that deal "ordinary" damage. It splits into three types you can resist on their own -- bash (heavy, crushing blows), pierce (stabs) and slash (cuts). Bash is by far the most common in the world, so resisting it protects you most often. Magic weapons or weapon flags have their own affect types -- usually elemental ones.
• Magic: effects of combat magic -- but not prayers
• Prayers: effects of most cleric and paladin prayers
• Elements: the effects of fire (e.g. fireball), cold (e.g. chill touch), electricity/shock (e.g. lightning bolt), acid, energy, light, sound, water/drowning, and mental attacks.

• Special: special affect types such as holiness (most benediction prayers), negativity (most maladiction spells), summoning and charm
• Materials: you can separately gain resistance or vulnerability to weapons made of certain materials. For example, elves are vulnerable to iron weapons, while rockseers are vulnerable to wooden ones.

You can learn a weapon's material or attack type through identification. You can learn a spell's or prayer's affect type through experience.

Many creatures (mobs) in the world already have innate immunities or vulnerabilities. You can find out exactly which ones only by fighting them with a specific affect type.