The Rage of Asmodai: Warhammer 40,000

Captain Vidarna of the Relictors leads a squad of his brothers in pursuit of a dark artefact on a world riven by heresy. But the appearance of Chaplain Asmodai of the Dark Angels changes his mission. The Dark Angel claims to have the relic they seek - but to claim it, the Relictors need to aid him in capturing the leader of the rebellion, a mysterious black-armoured Space Marine whose armour bears symbols similar to that of the Dark Angels themselves....