Algard

The Legends of Algard, the renowned Grey Wizard, are rife with half truths and fictitious tales, not surprising perhaps, for a practitioner of the Lore of Shadow. However, one enduring myth turned out to be true--Algard had achieved his collection of eldritch tomes into a fastness so well protected that it no longer truly existed on the mortal plane. Only Algard knew how to summon his keep and its treasures, but this secret was lost with his disappearance.

Towers of Screaming Death
Such is the haphazard nature of the Realm of Chaos, that now and again, during times when the Winds of Magic blow most strongly, Algard's towers reappear, materializing beneath the storm-blackened and unnatural skies. Sensing the presence of the arcane trove amidst the storm, the dreaded Chaos Sorcerer Mortabulous led his army and a host of monsters into the Empire to plunder the magical hoard. An army from Talabecland gathered beneath the storm to defend their land, well supported by a strong contingent of Battle Wizards from the Colleges of Magic in Altdorf.

Source

 * Warhammer Fantasy: Storm of Magic pg. 80