Shriven
The Shriven were once workers on the Forge World of Fortis Binary, however they were corrupted by Chaos. They were described as elaphantine, with long, nozzled gas masks sewn into their faces. They wore rubberised green body armour and the protectiver garb of their former workplace. Their armour was decorated with eye-aching symbols of Chaos.
The Shriven had no qualms about the use of poison agents, foul airborne gases that would boil the blood and fester the lungs. 1
They have got a rusty iron spike which they use to impale it at their victims at his chest. It was the sort of spike that the workers of the forge world would have used to wedge and manipulate the hoppers of molten ore in the Adeptus Mechanicus furnace works. They also cut out the hands and feet of their victims.2
The Shriven had erected Chaos altars at regular intervals into the trenches system of the battleground and each blackened factory bunker, storehouse and forge tower.3
Sources
1 First And Only (Novel) by Dan Abnett Part.Two: Fortis Binary Forge World. Capter Seven. 2 First And Only (Novel) by Dan Abnett Part.Two: Fortis Binary Forge World. Capter Eight. 3 First And Only (Novel) by Dan Abnett Part.Two: Fortis Binary Forge World. Capter Nine.