The Cult of Mekallis is anorder of Chaos sorcerers devoted to the worship of Tzeench, controlling the Daemon World of Hadstadt.
No one outside of the Cult itself knows what Mekallis is, but the Silver Order believes Mekallis was the founder of the cult, and now Daemon Prince of the worldthe cult now rules.
Nothing is known of the Cult of Mekallis before sometime in early M32 when the sorcerers took control of the world Hadstadt, converting it to a Chaos World devoted to worship of Tzeench.
After the discovery of the corruption of Hadstadt, an Imperial Army regiment attempted to cleanse the world, only to suffer horrendous casualties from the Warp Sorcery of Mekallis' sorcerers. As the Imperial Troops retreated, curtains of Warp Energy descended on the world: the sacrifice of the souls of their fallen comrades powered the transformation of Hadstadt into a Daemon World.
From Hadstadt, the sorcerers of Mekallis and their followers launch their own dark crusades - though a pallid shadow of those launched from the Eye of Terror, still they are supremely dangerous and armed with powerful Warp Sorcery. To combat these heretical crusaders, the Silver Order was founded; an order of Psychic warriors, they watch the borders of Hadstadt, fighting the Chaos-Worshippers wherever they may be found, occasionally launching attacks of their own against the Daemon World.
The Cult is a loosely organized group of sorcerers, each possessing his own fortress, followers, and each striving for his own power and the favor of their God.
The ruler of the Cult of Mekallis(and by extension, the Daemon World Hadstadt) is the Master Magister, most powerful sorcerer of the Cult. Although all members of the cult theoretically acknowledge his supremacy, all seek to overthrow him and seize power for themselves. The Cult is rife with intrigue; battles and even civil wars are not uncommon, and many sorcerers will launch their own invasions of the Imperium, seeking to attract followers and gain power to aid them in their eternal fratricidal conflict.
It is said that once Hadstadt was a thriving agri-world before Mekallis claimed it, but today it is a dark howling wasteland from which rise the spires of a thousand thousand sorcerer's towers. Surrounded by fluctuating fields of Warp energy, Hadstadt is both part of the materium and not, it cannot be conquered or cleansed, but only blocked off and besieged.