Colchis

Colchis was a world old beyond reckoning, its deserts studded with vast cathedrals and its cities crowded with temples, its every institution built around religious devotion. Its people were a faithful folk who lived by the pronouncements of a powerful priesthood and the words of ancient holy texts, and reverence saturated every corner of their crumbling, dust-blown civilisation.

Into this world of faith fell the daemon primarch-to-be Lorgar, discovered and raised amid the temples. He grew into a preacher of terrible conviction, and when he came to believe the old religion false he overthrew it in a holy war, tearing down the priesthood and raising in its place a new creed that foretold the coming of a god from the stars. When the Emperor arrived, Lorgar hailed Him as that very god.

The rebuke that followed, when the Emperor forbade Lorgar's worship of Him, wounded the primarch's soul and set him searching for other gods more willing to accept devotion. From Colchis and its faithful came the Word Bearers, the first Legion to fall, whose warriors carried the zealotry of their homeworld into the service of the Ruinous Powers.

It was Colchisian faith, turned from the Emperor toward the Dark Gods, that lit the first spark of the Heresy, for the Chaos Space Marines of the XVII Legion became the great apostles of damnation. In the age of retribution that followed the traitors' defeat, the Imperium is said to have unmade the world entirely, scouring the temple-planet from the stars as punishment for the heresy it had birthed. Colchis is lost now, its cathedrals silent, its faith turned to ash, a world that worshipped too well and was consumed by the god it found.