Chaos Spawn

A Chaos Spawn is usually a twisted and horrendous creature. Chaos twists everything in it's way. Some mutations of Chaos are "mild" but sometimes living things twist beyond normal life. Some are born this way some Beastman Shamans or Chaos Sorcerers have spells that change living beings into spawns. Also a creature which is visited by too many gifts of the Dark Gods may also eventually succumbs to madness and mutation and becomes a Spawn of Chaos.

The fate of a Spawn is to die, either on the field of battle by axe or sword, torn apart in the wilds by even more savage creatures, or literally ripped asunder by the Chaos energy that continues to course through its twisted body.

Source

 * Games Workshop webpage