Robo-daemons!

The Forge of Souls rewards a very few elite daemons with physical constructs to possess, enabling them to maintain a presence in the mortal realm almost indefinitely. In return they swear oaths of fealty to defend the Forge above all other allegiances should it fall under attack from forces of the chaos gods.

Most prominantly this eternal deal is spearheaded by the monstrous Soulgrinders, hybrid daemons mounted upon robotic lower bodies and legs. Little stands in the way of these giant warbringers on the field of battle, but their numbers are thinly spread and their sheer bulk prevents them from occupying various positions in daemonic forces.

Lesser daemon hybrids have been sighted alongside the Soulgrinders in the growing incursions. Creatures of all shapes and deformity, part robot, part warp abomination, these daemons seem to fulfil the role of infantry, marshalled into war by their larger brethren.