He is also known as Sumeros Summerking, the Blood-Rose Prince and Ushoran the Handsome.
It is said that he was originally a fair and favoured servant of Nagash but who fell from favour for reasons long forgotten and was transformed into a mockery of his once handsome form and was then condemned to prowl the Nightlands of the Realm of Shyish. However such was his rage, that he cut a swath through the lands and cities of that realm until his master imprisoned him in the Shroudcage.
Another story is told by the blood-children of Neferata who call him the Blood-Rose Prince and who state that rather than the Great Necromancer himself, it was his betryal of the Queen of Mysteries that led to his downfall and curse.
It was not until the Age of Chaos that he would be unwittingly released by Sigmar during his own war with Nagash. Fleeing to the shadows, the Carrion King found the first Mordants, depraved mortal cannibals, some of whom he then gifted with his blood and so the Flesh-eater Courts were born in all their bloody glory. It is said that Nagash still seeks him so that he might gain true control over the courts.