Frostfire

Frostfire refers to a type of magic wielded by mages. It is a multi-school, combining the Fire and Frost schools, even though these are often the opposite of each other. Multi-school abilities benefit from bonuses that affect any of their schools, use the lowest resistance value among their schools, ignore absorption and immunity effects that apply to only some of their schools, and can be used even when one or more of their schools have been locked with an interrupt effect. For example, Frostfire spells have the ability to apply both DoT's used by fire spells, and chills used by frost spells.

Equipment sets
A few equipment sets refer to Frostfire magic (although they do not use it in any way):
 * Inv chest cloth 43.png Frostfire Regalia
 * Inv chest cloth 43.png Heroes' Frostfire Garb
 * Inv chest cloth 43.png Valorous Frostfire Garb

History
"Frostfire" as something associated with mages was first mentioned as the name for the Frostfire Regalia set in vanilla WoW. However, the mechanic was not implemented until Wrath of the Lich King, with the introduction of Frostfire Bolt. Although the Frostfire school did not exist at that time, Frostfire Bolt's mechanics served as a prototype for the multi-school effect, dealing whichever type of damage the target was most vulnerable to. The school was officially introduced in patch 4.0.3a, along with the second Frostfire spell, Frostfire Orb. However, Frostfire Orb was later removed in patch 5.0.4, and Frostfire Bolt was removed in patch 7.0.3.