Angron

Angron was the primarch the Emperor could not save and would not free, a warlord forged not in a crucible of glory but in the fighting-pits of Nuceria, where he was raised a slave and made to kill for the pleasure of others. Into his skull his masters drove the Butcher's Nails, cortical implants that turned his every waking moment into a storm of pain and rage, and it was as a rebel and a doomed champion of the enslaved that the Emperor found him. Rather than stand with Angron's uprising, the Emperor plucked him away to command a Legion and left his comrades to be slaughtered. Angron never forgave the theft of his last, best death.

He led the World Eaters not as a father but as a fellow prisoner of the Nails, sharing his torment with his sons until Legion and primarch alike were bound to the same red compulsion. When Horus rebelled, Angron required no promise of power, only the war itself. Every battle fed the fury the Nails demanded, and every massacre drew him nearer to the Blood God who had watched him since Nuceria. His was a damnation that owed nothing to ambition and everything to pain, a slave who was never truly freed, only handed from one set of masters to the next.