From WoWWiki

This article or section contains lore taken from the Warcraft RPG books.

A fiery destroyer that kills an opponent with its slam attack or fire damage burns the creature utterly until nothing remains but ash. The resulting ash still provides enough of a focus for a resurrection spell, but the victim cannot be returned to life by any lesser method, including raise dead and reincarnation. A fiery destroyer can consume a dead creature but it provokes attacks of opportunity. The destroyer cannot consume dead creatures that were immune to fire in life.^{MG 59}