Over the centuries, half-sane scholars corrupted by Chaos have secretly attempted to decipher the purposes of the Great Conspirator. Most of their claims are contradictory. However, many mention the legend of the Great Game – a mythical contest of war and wits fought between the four Ruinous Powers. The Dark Gods ally with one another only when it suits them, and often fight against each other for the most spurious reasons. Tzeentch, Slaanesh, Nurgle, and Khorne constantly compete to become the most powerful of the Chaos gods. They are united only in their determination to destroy the civilised world.
The Great Game is played out in three arenas. Within the Realm of Chaos, the four gods send armies of daemons and the most powerful of their mortal champions to assault each other’s domains. However, the defences surrounding their infernal kingdoms are almost impossible to breach.
The second theatre is the Chaos Wastes of the mortal world, where warrior-wizards lead barbarian tribes and warbands loyal to Tzeentch against the mortal armies of the rival Chaos gods. The slaughter takes place on battlegrounds that constantly warp and change as a tempest of Dark Magic rages overhead. Battles are won and battles are lost, and no single deity ever dominates.
These battles are testing grounds for their champions, where the weak fall and the strong are prepared for the main arena of the Great Game: the civilised realms of the Old World. The Ruinous Powers try to entice mortals living in those realms to betray their birthright and worship Chaos, and command those they corrupt to sow anarchy and desecration.
Tzeentch will often use his Chaos cults to thwart the plots of those who follow the rival Ruinous Powers, but cults dedicated to Tzeentch also compete among themselves to attract the eye of their god. The Great Conspirator enjoys fostering treason and deception even among his own followers.
The cults prepare the way for an invasion of Chaos hordes not seen since the Great War Against Chaos. Even in the midst of that invasion, the Ruinous Powers competed to ensure that their own forces emerged dominant, and Tzeentch used all his cunning to obstruct the achievements of his brother gods. Over two hundred years later, rumours that the End Times are nigh can again be heard in the streets and taverns of the Empire.
Bands of roaming zealots loudly proclaim that doom is at hand, and the civilised nations gird for war against the north again. The countless battles fought between the Chaos armies in the Chaos Wastes have produced a mighty champion who bows to all the Ruinous Powers with equal respect. This is Archaon, whose ruthless feats have earned him the title Lord of the End Times. Under this warlord, the Ruinous Powers hope to unite their forces to finally destroy civilisation, though no doubt the Great Game will continue unabated, and the champions of the Chaos gods will challenge each other while the Old World burns around them.
Tzeentch’s ultimate goal is utterly unknowable. Perhaps the Great Game and even the destruction of the Old World are merely amusing diversions for the Great Schemer? The realisation of his greater plan, if he has one, is lost in the mists of the far future. His conspiracies often appear to be self-defeating and contradictory, for he has intricately planned each ineffable manoeuvre far into eternity. To even begin to unravel his intentions is to invite madness. Indeed it could be said that only the mad can truly understand the ways of the Great Schemer, for perhaps he is mad himself, and his plans are, in fact, utterly devoid of all reason.
Source
- Warhammer Fantasy RPG 3rd ED -- Book of Change
pg. 4