Undead were once-living creatures that had been animated by spiritual or supernatural forces. Some deities employed undead as divine servants.
Undead were extremely resilient to a number of effects and substances that were extremely harmful to the living.
There were six basic ways a living creature could become undead: Purposeful personal reanimation, Minions, Atrocity calls to unlife, Unfinished business,Dark forces and Death by wounds caused by another undead.