Interex

The Interex were a highly advanced interstellar human civilisation that existed across some thirty star systems at the time of the Great Crusade in the 31st Millennium. The Interex, unlike the Imperium of Man, had decided that the best way to deal with intelligent alien species was not to exterminate them or make war upon them, but to try and coexist with them. In fact, the Interex had become the close allies and nominal overlords of a simian alien species called the Kinebrach who they had integrated into their own society. The Interex ultimately became enemies of the Imperium after hostilities between the two human civilizations began when the Interex accused a diplomatic party of Luna Wolves led by the Warmaster Horus with breaking into their Hall of Devices, a museum on the Interex world of Xenobia dedicated to weaponry, and stealing a prized Kinebrach blade called an Anathame that was known to have links to Chaos. The Interex believed that the Imperium was allied to Chaos and never knew that in fact the weapon had been stolen by First Chaplain Erebus of the Word Bearers Legion, who had been with Horus' diplomatic party. Unknown to Horus, Erebus and the Word Bearers Legion had already turned to the worship of the Ruinous Powers of Chaos. The powers of the Warp had informed Erebus and his Primarch Lorgar that if they wished to bring Horus over to the side of Chaos, then they would need the Kinebrach Anathame. The Interex civilisation was ultimately wiped out by the Luna Wolves following the commencement of hostilities between the two human factions on the night Erebus stole the Anathame.