The Warp is home to more nightmares then just daemons. Within the Warp exist countless writhing entities, beasts of the warp, which have been born there or forged by using massive amounts of power. Tzeentch uses these beasts and changes them into forms by which the material universe might recognize and fear them. Thus he creates great hungry Leviathans as pets, creatures born of the hellish depths of mankind's imagination. Leviathans are huge warp creatures more massive then any battleship and wreathed in flame, that travel the warp just as space faring vessels travel the material universe.
When at a point of great power from local warp storms, sacrifices, and worshipers, Tzeentch may call forth enough power to send a Leviathan traveling from beyond the Immaterium, into the material universe. Riding upon the tides of Chaos which surround the war fleets of Chaos and buoyed along by the surging waves of magic and eddies of unreality which Tzeentch's followers bring in their wake. Leviathans are followed by swarms of Screamers and other space-faring daemons. Such unreality not only disrupts and warps space around it, but also the Warp and the Webway as well. They fall upon ships like great predators, rending metal, chitin, flesh, and souls apart with equal ease. After time, however, Leviathans must return to the Warp that spawned them, leaving behind damage on an enormous scale.