During the Stygian Wars the Stygian empire showed a remarkable success at boarding actions that resulted in the loss of Imperial ships. The reason for their high success rate was only realized later when survivors spoke of marching metal monstrosities. Later as these armored suits began making appearances on battlefields across the Stygian Wars would they be identified as cataphractii.
Cataphractii operate in a similar manner as helbrutes and dreadnaughts. They are however no where near as heavily armored, far smaller, and easier to build and crew. A single human crews these armored walkers after having his limbs removed and being cyberneticly grafted to the machine. Thus heavily armored and with enhanced mechanical strength these cataphractii carry heavy weapons with ease across the battlefield.
Cataphractii typically are armed with either rapid fire grenade launchers or assault cannons. Immune to most small arms fire they are ideal shock troops in a boarding action or spearheading an infantry assault. Their ease of manufacture means that three cataphractii can be created in the time it takes for a single dreadnaught to be created. The cataphractii design was deemed unclean and heretical by the followers of the cult mechanicus. They were seen in increasing numbers throughout the Stygian Wars, and their presence often betrayed an intent and purpose by Stygian commanders who assigned them only to the warzones they felt were most critical.
The walker model shown above is from the Dust range.