The Scintillating Legions (sing. Scintillating Legion) are the daemonic armies of the Chaos God Tzeentch that exist within the Realm of Chaos. They sometimes manage to be summoned or force their way into the Materium under the right conditions to pursue the endless schemes of the Changer of Ways among the worlds of Humanity and xenos alike.
The air fills with kaleidoscopic bursts of magical energy as the convocations of the Great Conspirator's Daemon armies materialise for battle. To mortal eyes, the different daemonic legions of Tzeentch are impossible to distinguish, each one as bizarre as the next, yet there is method within the madness -- although none save the Architect of Fate himself could truly comprehend it.
While Tzeentch prefers to further his ends through sorcery or schemes, there will often be no better alternative than force to achieve his goals. Thus are Tzeentch's Daemon legions deployed, armies unlike anything seen in realspace.
These convocations go to war in a capering, bounding, spell-wielding carnival of violence, obliterating foes with hellfire and change-magics. Unlike the militant cohorts of Khorne or the cyclical forces that serve Nurgle, Tzeentch's legions are often in flux, shifting composition or altering tactics to better serve their master.
Each Scintillating Legion is commanded by one of Tzeentch's Greater Daemons, a Lord of Change, each utterly dedicated to their master's cause. A Lord of Change is granted great independence to operate, and with the help of their advisers and champions, they will command a legion suited to their own proclivities.
Those that love to bask in the glow of destruction might head a Conflagration Legion -- a force centred around formations of Flamers, capable of wielding the most powerful of Warp-flames.
Others favour the Legions Anarchus, which are far less predictable in composition and specialise in sudden and wholly unexpected incursions.
Those Greater Daemons of Tzeentch who are masters of duplicity will lead one of the Veiled Legions; the most mysterious of Tzeentch's forces, these surface rarely and are almost never brought to battle, and slip off unseen after their plan's culmination.
Each of Tzeentch's daemonic legions is divided into nine hosts, and these are directed in battle by Daemon Princes and Heralds such as Changecasters, Fluxmasters and Fateskimmers. The leaders of the hosts compete to attract more praise from the Lord of Change that commands them, and even between the legions, there is no end to the machinations as rival Lords of Change plot against one another and sabotage each other's plans. It is another game within the Great Game, and one beloved most by the Great Schemer himself, who frequently weighs the tributes paid to him and proclaims his judgement.
Thus do the sigils of each Daemon legion dance across the Pyramid of Yrch deep in the Crystal Labyrinth of the Realm of the Sorcerer, blazing into a new order of countenance. It is a hierarchy that moves often, but the nine most favoured daemonic legions are each granted control of one of the Fractal Fortresses that tower over the Crystal Labyrinth, an honour all Tzeentch's servants desire to attain.
- Codex: Chaos Daemons (8th Edition), pp. 14-17