Stygian Bastion

Although they are similar to Imperial bastions, those captured and constructed by the Stygian Empire differed in a number of significant ways.  While they retained the four heavy bolter mounts, Stygian bastions often included Havoc launchers mounted on the battlements.  Additionally they often had missile launchers and plasma cannons firing ecto plasma added.  These cannons drew their energy from the bastion itself.
Stygian Bastions appear to be partially possessed.  This allowed them to fuel the plasma cannons and accounts to the energy nodes with screaming faces along with the bleeding walls.  The supposed possession of such bastions also greatly aided the ease with which summoning could be performed.  One bastion in particular seemed to harbor malignant life, the so called Verden Bastion famous for its self repairing walls, mass daemonic incursions in it's presence.  It was observed the greater the carnage the stronger it became.
Stygian Bastions served as defensive bulwarks and also as places of worship.  Many of these bastions contained pulpits with heretical tomes on them to preach to the masses. 

Standard GW kit with bit's added from the chaos accessory sprue, the forgefiend kits, and Helbrute kits.