Raid on the Emperor's Scions

The Raid on the Emperor's Scions was a lamentable event that occurred in the annals of Imperial history, when the Emperor's Scions Space Marine Chapter was set upon by a mysterious Heretic Astartes force that overwhelmed and eventually destroyed them. It is believed by Imperial scholars that these mysterious attackers were none other than the Keepers of Equity Chaos Warband.

History
Finally, and by far the largest breakthrough within the imperial intelligence community, occured in late M39 when the Emperor's Scions Space Marine Chapter transmitted an urgent distress call, claiming that their Chapter's space hulk/fortress-monastery was under attack from an unknown force, and their thousand-strong force of Astartes had been whittled down to just under two hundred within a day. Astra Militarum and Adeptus Astartes Chapters quickly responded to find the supposed space hulk base cut cleanly in half by an unknown force. With no trace of the enemy, Imperial forces surveyed the wreckage finding only empty armor and standard issue Astartes weaponry. The chapter master however held information crucial to the identification of the Keepers - in his dying moments he had come face to face with the leader of the group and recorded a final message for their mysterious destroyers.