Cold Mastery

 is a Sorceress Skill in Diablo II. It decreases enemy Cold Resistance.

Lore
''Once mastery over this powerful elemental force is attained, a Sorceress achieves perfect command over this school of magic. Her freezing spells are now of such potency that those adversaries formerly impervious to their effects soon find themselves the surprised victims of a vicious, chilly assault. ''

Synergies

 * Gives synergy to: None
 * Receives synergy from: None

Cold Mastery reduces the resistances of hostile monsters and players. Cold Mastery only applies to the Sorceress; that is, when fighting on a team, only Cold Spells cast by the Sorceress with the skill receive its benefits. It works on other Players in PvP, even if their resistances are maxed out.

However, Cold Mastery does not affect monsters that are Cold Immune. Enemies that are not Cold Immune can have their Cold Resistances lowered below zero, making a Sorceress' Cold Spells especially effective, but the only ways to break resistances are the Necromancer's Lower Resist and the Paladin's Conviction aura.

Cold Mastery is a direct subtraction modifier from the enemies' resistance, so if a target has 75% Cold Resistance and the Sorceress has only the first level of Cold Mastery, the target's resistance will be 75% - 20% = 55%. Cold Mastery reduces cold resistances to -100% by level 17. As resistances cannot fall below -100%, extra points after level 17 only reduce resistances for monsters that had resistances to Cold in the first place. Extra points in Cold Mastery become completely pointless past level 37 (to the point where even creatures with near-immunity to cold has -100% cold resistance), although the lack of monsters with such high cold resistances make investing in the skill relatively superfluous after level 27 (where cold resists are at -150%).

Lightning and Fire sorceress's who specialized in cold skills only secondarily will often find their cold skills being their most potent upon reaching the highly-resistant creatures in Hell difficulty, due in no small part to Cold Mastery.