Undead

Undead are beings who have been raised into the state of undeath. The Undead Scourge and Forsaken employ undead soldiers in their armies.

Undead-Specific Races

The Scourge are a race of undead originally created by the Burning Legion as a weapon to assist their invasion in the Third War, but went rogue after the Battle for Mount Hyjal and planned to destroy all life on Azeroth. They are currently inactive and being kept under control by the Lich King.
The Forsaken are a group of mainly human undead that broke free from the Scourge and joined the Horde, lead by Sylvanas Windrunner.
The Risen are a faction of undead in Stratholme lead by Dreadlord Balnazzar, consists of risen Scarlet Crusaders who plan on taking the Plaguelands for the Burning Legion.
Cult of the Damned are a cult that served and swore oath to the Scourge and the Lich King. Their xurrent whereabouts are unknown.
Rotbrain Undead are a group of rogue undead that tried to break away from the Forsaken, and are currently destroyed.
The Knights of the Ebon Blade are an order of death knights formerly loyal to the Scourge which now serve as a neutral orginization with members sworn to both the Grand Alliance and New Horde.