The Undying Legion

The Undying Legion is the name of the excoriation campaign conducted by the merciless Emperor's Reapers Space Marine Chapter upon a long-lost world enslaved by a malevolent and ancient Artificial Intelligence constructs, known as the 'Men of Iron'.

Background
Members of the Emperor's Reapers' 7th Company led by Captain Agros teus discovers another world lost since the Dark Age of Technology, but unlike the world of Helias, all traces of the inhabitants show that their cities were abandoned, with no presence of any Dark Age voidcraft and skeletons long decayed. After further exploration the company discovered the world's dark secret - it was, in fact, a prison for the ancient A.I. ('Abominable Intelligence') constructs known as the Men of Iron. They been reactivated during a civil war that took place on the very same planet. Although the survivors managed to seal the Men of Iron away deep underground they are unable to deactivate them. In hope that to avoid the day when this evil automata broke free, Agros seized the initiative and led the charge straight into the prison to wipe them all out. After a deadly battle only one survivor remained, the 2nd Squad's Techmarine Katos Ironbones. Though severely wounded, he managed to make his way back to the planet's surface, clutching the metal skull of the leader of the Men of Iron, and called for help. Fortunately all the equipment and some of the fallen's gene-seed was recovered. Due to the severity of the injuries Katos received during the conflict, his body was interred within a chassis of a Contemptor Pattern Dreadnought. After the Chapter departed the planet's surface, they subjected it to an Exterminatus warhead to ensure that all traces of the malevolent A.I. was wiped from existence.