The Iron Circle are Perturabo's personal guard, a phalanx of hulking battle-automata built to stand where the primarch trusted no living warrior to stand for him. Forged in the IV Legion's own foundries and bearing great domed shields alongside their weapons, these robotic sentinels were designed to absorb punishment that would fell a dozen legionaries and to protect their master with a loyalty untainted by the doubts and grievances that plagued flesh-and-blood warriors.
That Perturabo should surround himself with unthinking machines rather than his own sons spoke volumes of the bitterness that had settled over the Iron Warriors, a primarch so wary of betrayal that he engineered his own incorruptible bodyguard. In battle the Iron Circle advanced as an unbreakable wall around Perturabo, crushing all who approached beneath weapon and tread. During the Heresy they became a fixture at their master's side, silent iron witnesses to the IV Legion's descent, and a barrier of adamantium between the Lord of Iron and a galaxy he had come to trust not at all.
Order of battle
