This shows an Inquisitor, an Assassin from the Vindicare Temple who are expect markmens and what i believe is a Sister of Battle (although it could be another Inquisitor) fighting of some Blood Letters, which are lesser Demons of the Chaos Blood God Khorne. The Inquisitor is either from the Ordo Malleus which is the demon hunting arm of the Inquisition or from the Ordo Hereticus the heretic and witch hunting arm. The reason i dont automatically say his from the Ordo Malleus is because its possible these demons were summoned by some heretic his trying to track down. Which would explain the assassin as well.