Excommunicate Traitoris

Excommunicate Traitoris is the term used in reference to the highest form of reproach against an organisation that has committed extreme acts of heresy, unforgivable acts against the Imperium or mutation. This fate may also befall individuals whom committed similar acts of heresy. It is the ultimate form of censure: banished from the human race and cast from the light of the benevolence of the beloved Emperor of Mankind. There is no graver fate for those that serve the Imperium. When an individual or organisation is declared Excommunicate Traitoris by either the Senatorum Imperialis—the High Lords of Terra or an Inquisitor of the Holy Ordos, the accused is struck from the annals of Imperial history. Their names deleted from the scrolls of honour in the Hall of Heroes and wiped from the memories of the Archivum Imperialis. If the accused is an individual battle-brother or an entire Chapter of Space Marines, their Gene-Seed will be destroyed and their bodies incinerated so that their blood will no longer taint mankind. The Imperium of Man will forever turn their backs upon them. If the accused confesses and repents their misdeeds, their deaths shall be quick. But more often than not, the accused traitors flee for their lives, most often towards the hell-storms of the dust wrapped nebula known as the Eye of Terror. With no sanctuary to be found within the realms of man, they will be forever hunted for the rest of their days or executed on sight. Either way, their lives will eventually end for their sins against the Emperor.

Source

 * Bleeding Chalice (Novel) by Ben Counter
 * Codex Imperialis (2nd Edition)
 * Inquisitor (Novel: re-released as Draco) by Ian Watson