Kyriss - Signus Campaign: For untold generations, the Signus Cluster had been a centre for Human civilisation. Great hive cities littered the seven worlds of the Cluster and huge industrial complexes burrowed into the fifteen moons. But amongst the uncounted millions settled within the Signus Cluster lurked sinister Chaos Cultists.At the onset of the Horus Heresy, Warmaster Horus sent a messenger aboard the Word Bearers vessel Dark Page to a mustering of the Blood Angels Legion, informing Primarch Sanguinius that the worlds of the Signus Cluster had gone dark, with no further communications with the wider Imperium due to the reemergence of a hostile xenos species called the Nephilim, thought to have been destroyed by the Blood Angels, Luna Wolves and White Scars Legions during the Great Crusade.Horus called for the Blood Angels to respond in force to the return of this threat, and Sanguinius agreed, mustering the bulk of his Legion along with the Word Bearers on the Dark Page and an unexpected contingent of Space Wolves that had joined the Blood Angels fleet on the express command of Malcador the Sigillite, the Regent of Terra, to ensure that Sanguinius remained loyal to the Emperor. In reality, however, the message was a trap. Horus hoped that the Blood Angels and Sanguinius would be either destroyed by the Chaos forces he knew to be already operating in the Signus Cluster or be corrupted by them to his side. Either way, a powerful Loyalist Space Marine Legion would no longer be able to interfere with the Warmaster's plans to betray his father, the Emperor of Mankind, and launch an offensive against Terra to overthrow His rule.In the Signus Cluster itself, there had been an outbreak of unexplained phenomena over the course of several solar months. The worlds of the system were suffering from a massive increase in birth defects and mutations, inexplicable meteorological patterns and the mysterious deaths of the astropaths assigned to the Imperial colonies of the cluster. The colonists had called for help, appealing to the Administratum, the Imperial Army and even the Legiones Astartes for aid.Eventually, help appeared to arrive in the form of a man named Bruja, an emissary of Horus, whose betrayal of the Emperor still remained secret at this time. Bruja was in truth an agent of the Chaos Gods, a native Davinite and a priest of the Temple of the Serpent Lodge that had corrupted the Warmaster to the service of the Ruinous Powers. Soon after his arrival in the system, the priest's possessed form burst apart and allowed the Slaaneshi Keeper of Secrets Kyriss the Perverse to enter the Materium in the Signus Cluster.Within solar months, Kyriss and the agents he soon suborned infested the rabble of the Signus Cluster and in their teeming numbers hid the witch-cabals that later summoned more Daemons to Signus. When these agents and Chaos Cultists received a signal from Horus not long before the Isstvan III Atrocity in 005.M31, they rose up in a violent insurrection and seized power within the Signus Cluster, summoning Daemons into realspace to lead them and rule over the star system.Daemons soon stalked the hive cities and established foul palaces across the entire star system. The Human population of the Signus Cluster was enslaved, reduced to fodder for the minions of Chaos. Powerful summoning spells cast by the witch-cabals allowed the Daemons free reign over Signus. In addition to this, thousands of Signan psykers had been possessed by Warp entities and become Daemonhosts.The Signus Cluster had become a veritable extension of the Realm of Chaos within the Warp in only a short time, and a demesne of Daemons. Kyriss the Perverse now ruled the Signus Cluster. Once the cluster's primary world was under the control of Chaos, Kyriss raised for itself a great palace on Signus Prime that it named the Cathedral of the Mark. This blasphenous edifice was crafted from the bones of every man, woman and child murdered by the servants of Chaos on Signus Prime.Then the Daemonic legions under Kyriss' control swept from Signus Prime across the rest of the system, destroying the work of millenniums of Human civilisation and eradicating the populations of whole worlds. Almost the entire population of the Signus Cluster was enslaved, corrupted to the service of Chaos or just butchered outright, and hope fled from those few who survived.The 7 worlds and 15 moons of the trinary system were soon in thrall to this mighty Daemon lord and its teeming hordes. The Daemons were aided by the machinations of the Chaos Cultists. These bands of madmen opened their worlds to the creatures of the Warp, conjuring powerful summoning spells and offering themselves up for possession.The rest of the Human population of Signus Cluster had been annihilated or enslaved, their only fate to be consumed by the horrors of the Warp. The entire star system became a charnel house, a place of evil and a home for the creatures of the Immaterium. There was never so base a betrayal as this one, for Sanguinius looked to Horus as a brother, and never would have believed he, his Legion and literally billions of people would be sacrificed to the foul denizens of the Warp.Such it was that the Blood Angels Legion fleet entered the Signus Cluster unaware of what they were to face. Ultimately, the Legion made an unexpected planetfall on Signus Prime, the primary settled world of the system where Sanguinius confronted one of the architects of the slaughter -- the mighty Bloodthirster Ka'Bandha.After a climatic battle with Ka'Bandha, in which the Bloodthirster was forced howling back into the Immaterium, Kyriss schemed against Sanguinius and attempted to tempt the primarch with a devil's bargain -- he would spare the Angel's gene-sons from both the Red Thirst and the Black Rage if Sanguinius was willing to sacrifice himself, to take the incessant rage within him and step into the Realm of Chaos.But Kyriss' plans were foiled when the Blood Angels Apothecary Meros volunteered himself in his gene-sire's stead, becoming the Daemonic entity known as the Red Angel in the process.Enraged at the loss of one of his sons, and to honour Meros' noble sacrifice, Sanguinius sliced Kyriss' head from his body, sending the Greater Daemon of the Dark Prince screaming back into the Warp to face the displeasure of his dark master.