Sar'tir is a Lord of Change, a Greater Daemon of Tzeentch who rules one of the most infamous planets of the Cat's Cradle, a region of space caressed by Warp currents and tendrils of the raw Immaterium seeping forth from the boundary of the Inner Ring of the Screaming Vortex, one of two massive Warp Storms which separate the Calixis Sector of the Imperium of Man from the Koronus Expanse.
Though the Eye of Terror is possibly the largest and most well known area of Warp space intrusion, multiple others are scattered around the galaxy. The Screaming Vortex is one such anomaly, born of the same cataclysm which ruined the Eldar civilisation and created the Eye in its wake. The Imperium knows next to nothing about the Screaming Vortex, and what little its agents do know indicates only that there are some inhabited worlds in the outer edge of the maelstrom. Dubbed the Gloaming Worlds, they are the more civilised and developed worlds in the Vortex.
Within the deepest recesses of the Gloaming Worlds lies a region of space known as the Cat's Cradle. This area is a playground for daemons and powerful Sorcerers, speckled with dozens of worlds -- some that orbit stars normally, others drifting alone in the void. A number of these worlds are merely illusion, a glamour cast upon the void to fool the eye and sensors of any passing being or vessel. Plagued with trickery, illusions, and deceit, the worlds of the Cat's Cradle are places where logic and solidity can no longer be counted upon. This region is ruled only by the whims of those beings powerful enough to establish their own domains within.
Perhaps one of the most infamous planets of the Cat's Cradle is the home of a Greater Daemon of Tzeentch, a Lord of Change known as Sar'tir. This Lord of Change and a coterie of Shaper-Artisan Sorcerers from Q'sal created a baroque and twisted world built entirely as a theatre. Called "The Farce," the world consists of ever-changing vistas of stages, stadiums, and amphitheatres. Each theatre is connected to the others by gravity-defying corridors, staircases, and tunnels constructed at impossible angles. The planet is inhabited by seemingly endless rows of silent observers surrounding each stage. The audience is rarely known to move or speak, their purpose focused upon the players and the scenes acted out. Sar'tir takes great pleasure in putting on elaborate pantomimes that mimic foibles of Human and Eldar civilisations. These caricatures are acted out by captives from across the galaxy, representatives of many different races and creeds. Enchanted chains are wrapped around the actors' bodies, forcing them to work their way from scene to scene or face waves of searing agony or death, consumed by eldritch fires. Sar'tir seems to enjoy the shows put on by the most recalcitrant and resistant actors, cackling wildly with glee as Imperial Inquisitors and Chaos Space Marines alike grind out their lines through clenched jaws and stiffly move to their allotted positions upon the stage.
One of the most welcoming worlds of the Cat's Cradle, the Farce offers many pleasures and perquisites for visitors that pass a series of simple tests. Those who fail or refuse to submit to the testing are added to Sar'tir's collection of performers, for such is the price of attendance charged. From time to time, the Lord of Change extends special invitations to particularly powerful daemons and warlords within the Screaming Vortex to witness his latest masterpiece and observe his newest captives in the throes of their forced levity. Sar'tir's knowledge of plays and pantomimes is seemingly inexhaustible, and there are a number of secrets hidden within the most ancient and rare performances that are displayed within the Farce. News of such a show draws many visitors despite the planet's particular dangers. Rumours have spread throughout the Vortex that Sar'tir has somehow acquired a troupe of Harlequins, and he intends something truly special and significant for these Eldar -- a performance of his own creation that promises to reveal hints about many of the most obscure enigmas.
- Black Crusade: The Tome of Fate (RPG), pg. 94