Iron Warriors were the IV Legion of the Legiones Astartes, led by Perturabo – a master strategist and architect of destruction. They hailed from the planet Olympia, where Perturabo learned the art of siegecraft and a hatred of weakness. Their expertise lay in fortress warfare, war machines, and unyielding tactics.

The Iron Warriors were the Imperium’s finest siege masters but felt perpetually unappreciated. Their rivalry with the Imperial Fists and Rogal Dorn bred bitterness that ultimately led them to join Horus. During the Heresy, they played a key role in the Siege of Terra, where Perturabo designed the assault on the Imperial Palace.

In the Horus Heresy game system, Iron Warriors feature rules such as Wrack & Ruin and Siege Tyrants, emphasizing heavy firepower and devastating precision. Their forces include Tyrant Siege Terminators, Iron Havocs, Warsmiths, and heroes like Narik Dreygur, Forrix, and Perturabo himself.