Marabas is a Lord of Change, a Greater Daemon of the Changer of Ways Tzeentch. Marabas was once active in the Calixis Sector and his machinations helped to oppose the Angevin Crusade that initially brought the sector under the control of the Imperium. Eventually, the Inquisition moved against the daemon on the world of Malfi and banished him back to the Warp. But Marabas hungers for revenge and the Calixis Sector will be the canvas upon which he works his bloody will.
Upon the Hive World of Scintilla, the capital world of the Calixis Sector that lies deep within the Segmentum Obscurus, is Hive Sibellus. The most notable landmark in this hive city is the Tricorn, the palace of the Inquisition. Composed of a dark and austere trio of linked towers at the northern end of the hive sprawl, the Tricorn is the headquarters of the High Council of the Calixian Conclave, the de facto administrative seat of the Inquisition in the sector. Within the deepest vaults of the Tricorn's Librarium lies ancient, dusty tomes that chronicle the Inquisition's initial forays into the newly discovered region of space that would eventually be known as the Calixis Sector. Amongst these ancient records, there is one tome that speaks of the Inquisition's battles against the Greater Daemon known as Marabas, a despicable servant of Tzeentch known as a Lord of Change.
For whatever reasons, the Daemon Lord plotted his machinations against the Imperial Angevin Crusade that brought the Calyx Expanse into the Emperor's light, inspiring heathen worlds encountered by the Imperial forces to resist the interlopers. He also incited pacified worlds to rise up in rebellion across the sector, igniting insurrection on a massive scale, causing unheard of levels of death and destruction. The Inquisition was hard-pressed on nearly a dozen worlds as they attempted to stamp out the Heretic cults and agents of Marabas. They eventually tracked the Greater Daemon to the Hive World of Malfi where the foul creature was slain through the valiant sacrifice of the Daemonhunter Zaalin as she rammed her gun-cutter into the hive-spire the Daemon occupied. In the wake of the devastation, Zaalin’s surviving followers invoked the rites of banishment, exiling Marabas to the Warp for 1,000 Terran years and a day.
Over the next millennia, the Inquisition has largely forgotten its past battles with the vile daemon, its attention drifting to the more important matters of the present day. However, the same cannot be said of Marabas, for during its centuries of exhile, the daemon has nursed a great grudge against those it deems responsible for his lamentable fate. The creature's banishment has now, however, come to its end. Marabas now prepares to bathe the entire Calixis Sector in the blood of innocents and fire once more.
- Dark Heresy - Ascension (RPG), pp. 204-205