A Chaos Boon, sometimes called the gift of the gods, is a mutation bestowed by the Dark Gods upon their most devoted or successful champions. To slay a mighty foe or perform some great atrocity in the name of Chaos may draw the attention of the Ruinous Powers, who reward their servants with alterations to flesh, mind, and soul.
Such gifts are capricious and rarely what the recipient might wish. A warrior of the Chaos Space Marines might be granted crackling daemonic strength, an extra limb bearing a hungering maw, or scales that turn aside blades. Yet the same power that elevates one champion may reduce another to a gibbering, formless mass, for the gods delight equally in the exaltation and the ruin of those who serve them.
The ultimate boon is ascension to daemonhood, the transformation of a favoured champion into an immortal daemon prince. The ultimate curse is to be twisted into a mindless Chaos Spawn, a fate that awaits any who accumulate too many gifts without the strength of will to bear them.