The Realm of Chaos is inhabited by the Chaos Powers and their minions, bt the shadow-selves of mortals, and by unsure flittering creatures born from the recurrent emotions of the once-living. It is a hell of sorts, and a heaven of sorts, and endless sea of heavens and hells. It is inhabited by numberless hunters and killers, things that prey upon the flittering creatures and even upon the shadowy spirits of men. Not the least of these are the shoaling Discs of Tzeentch, also known as the Steeds of Tzeentch. They roam the tides of the warp like shoals of daemonic barracudas, searching for the vulnerable things that inhabit it. The Disc shoals are vicious and uncaring hunters. They can scent the shadow-self of a vulnerable human, and will quickly find it and tear it to pieces, carrying the shattered remnants back to their Lord Tzeentch.
A Disc of Tzeentch
In the Realm of Chaos Discs are smoky creatures whose shifting forms hint at a profusion of teeth and penetrating little eyes. When they move into the material world at the command of thier Lord Tzeentch, their raw magical bodies assume bizarre and unlikely forms. While most are round and disc shaped, some are covered in eyes, and others sheathed in living metal. They fly through the air, darting and turning through the firmament like sleek fish through clear waters. A Champion or other servant of Tzeentch may be given a Steed of Tzeentch to ride through the air by standing upon its flat upper surface.
Because Discs exist primarily in the Realm of Chaos, only entering the material world under the direction of their daemonic superiors, they can re-enter the Realm of Chaos at will. In this way they can carry a Champion of Chaos into the Realm of Chao as a Warp Rider. However, mere mortals were not meant to exist in this immaterial universe and the exhilaration and sheer excitement can sometimes prove beyond human tolerance. The warp ride is the ultimate human experience- to be chased by the things that live within it, and sustained by the liquid ari of pure magic, to return to the mortal world at a pitch of ecstacy, every nerve burning with energy of raw magic.
The winds of magic screamed and laughed around him. Faster and faster the sky-shark twisted, higher and higher he rose upon a pinnable of fiery ecstacy. At last he realised what extraordinary power lay in the moment, and in a moment the thought was gone and all was speed once more. His body shook in spasms and around his feet the sky-sharks snapped, their skins glistening as magical sea spray burst over their flashing bodies. His scalp tingled and buzzed - the moment would last forever - but soon the sky-sharks would overtake hima and tip him into the waves of the warp. He laughed about and a thousand daemos heard his cry and turned as he tumbled and was lost laughing amonst the foaming pack.
Disc Riders
The Discs of Tzeentch are magical creatures which normally swim through the Realm of Chaos on the tides of warp space, hunting in shoals for vulnerable souls to prey upon. In the material universe they take the form of bizarre disc-shaped creatures which skim through the air, darting and turning like sleek fish. A Champion of Tzeentch may be given one of these sky-sharks to ride into battle by standing on its flat upper surface. Taken from Renegades