You ask why we must cleanse the Xenos. I will tell you. The filth of the alien and the witch must be exterminated to preserve the purity of the Human race, lest we degenerate into abomination.

– Witch Hunter Tyrus at the Conclave of Vera

The Monodominants are one of the oldest Imperialist sects. It was Inquisitor Goldo in the third century of the 33rd millennium who penned the treatise ‘Monodomination – The Right of Man to Rule the Galaxy in the Emperor’s Holy Name.’ In this lengthy document, he compiled his many experiences and commentaries from nearly four hundred years of service to the Imperium. His final conclusion amounted to declaring that the only way the Emperor’s loyal servants would survive in the galaxy was if everything else was destroyed. At the time, this overtly pessimistic view found few sympathizers and was attributed to a devout but aging Inquisitor suffering a breakdown and losing his faith in humanity’s ability to prevail. However, several centuries later, Inquisitor Jeriminus of Paelutia revived the theme of Monodominance and swore to enact Goldo’s vision, and it has enjoyed various levels of popularity ever since.
The Monodominants have a simple goal: to destroy forever the Emperor’s enemies. Monodominants have absolutely no tolerance for any kind of wayward behavior. There is no excuse for heresy, contemplating heresy, or for abetting heretics. Heresy includes mutation, religious deviation, aliens, psykers, and any other beings who do not conform to their view of the loyal Imperial servant. There is only one punishment for heresy in the Monodominant philosophy – death. Mankind is fighting a war for racial survival, and the Monodominants hope that if they kill off enough aliens, psykers, mutants, and heretics, eventually natural selection will prevail and humanity will rise to its position of ultimate power.
Monodominants are very militant and petition the Inquisition for the final solution of Exterminatus more than any other sect. They are an open faction, using their presence to stir widespread xenophobia and hatred, leading mobs of the frenzied citizenry to purge their own ranks of the filthy and unclean heretics who threaten their future. They are utterly ruthless and unforgiving, inflexible and intolerant. They are generally the youngest and most hot-headed of the Imperial Cult, charging across the Imperium leaving devastation in their wake. Their confidence in their philosophy is almost unshakeable and they, more than any other faction, will wage war upon sects with a slightly less hard-line view if their paths cross – in their minds, quite rightly, being a member of the Imperial Cult is no excuse for heresy.
Those who believe in the Monodominant philosophy are wont to associate with the most militant and violent cults and creeds within the Imperium, such as Redemptionists, and can most readily draw upon the resources of the Ministorum to achieve their aims. Of course, many find the Monodominants incredibly narrow-minded and rigid and claim that often they do more harm than good with their excessive purges. Those who believe in the incorporation of alien technology and warp artifacts, and other supposedly heretical notions, consider the Monodominants to be crippling themselves by their refusal to make use of such tools.