Kor Megron, the Reaper of Rhodax, was a Daemon Prince who had once been a mighty Space Marine of the Word Bearers Traitor Legion during the Horus Heresy. In later eras, after his ascension to daemonhood, Kor Megron continued to plague the galaxy with his foul presence.
The Word Bearers were once renowned for their fanatical loyalty and religious zeal in persecuting the enemies of the Emperor of Mankind. But when the Warmaster Horus, the greatest of the Primarchs and the Emperor's most favoured son, betrayed his oaths of loyalty and launched a galaxy-spanning insurrection against the Imperium, the once-loyal Word Bearers were one of the first Legions to openly declare for the Warmaster. They turned their adoration and devotion to the "False Emperor" towards the unholy pantheon of the Chaos Gods. They betrayed all that they had striven to build, ripping down the temples and edifices dedicated to the saviour of Mankind, bringing untold numbers of blasphemies and sacrilege across the length and breadth of the nascent Imperium of Man.
Following the defeat of Horus, Kor Megron continued to fight the Long War against the hated "Corpse Emperor", seeking to undo all that he had wrought as a once-loyal Astartes. The Dark Apostle led his Word Bearers Host in a bloody Dark Crusade across the galaxy for millennia. It was upon the Cardinal World of Rhodax that Kor Megron would perpetrate his greatest work and be granted the boon of daemonhood by the Ruinous Powers. The vile Dark Apostle fought a brutal war of attrition over a period of 3 months against a pitiful number of soldiers of the Imperium. As the streets of Rhodax filled with bloated corpses, Kor Magron's Bolter ran dry. He continued to fight on towards the Basilica of Petch, a shrine devoted to a beloved Imperial Saint to whom the world now looked for salvation. He slew the servants of the Corpse Emperor with his ancient Power Sword until the energy cells powering the weapon ran out and the blade had snapped off in the spine of a shambling Ogryn. Not dissuaded by this temporary setback, Kor Magron continued to fight on with his armoured fists.
Together with his warband he assailed the Imperial defenders on the steps of the fallen temple. The 14th Cadian Shock Troops Regiment of the Imperial Guard attacked the warhost en masse, 2,000 of their soldiers storming the marble staircases of the basilica, but the Word Bearers pushed them back. Though many of the remaining Word Bearers were wounded and they were running low on ammunition, they remained unbowed. While his men continued to fight, Kor Megron toppled the forty-foot tall statue of Saint Petch, piling the bodies of the Cadian dead around it to form a blasphemous mound upon the consecrated ground of the basilica.
Now bolstered by agents of the Inquisition, the Cadians attacked once more. Kor Megron stood upon the mound of the dead, roaring his devotion to the Ruinous Powers, offering up the piles of Imperial dead as a dark sacrifice. For his unflinching loyalty and dedication to the Chaos, the lords of the Warp rewarded their devoted servant with ascension to daemonhood on the spot. Seething with barely restrained power, Kor Magron's body transformed, twisted by the warping power of Chaos. Where once had stood a proud and strong Chaos Space Marine now towered an almighty Daemon Prince.
The Word Bearers roared their exaltation at their lord's transformation, fighting on with renewed vigour, for they had been blessed by the Dark Gods. The Daemon Prince ripped the marbled blade free from the statue of Saint Petch, and transformed it into a twisting and corrupted weapon of cruel destruction with his newborn Chaotic powers. Kor Magron strode forth and wreaked terrible slaughter upon the Imperial defenders of Rhodax. Soon after, Rhodax was declared a Dead World by the Inquisition, drifting lifeless in the void of space, a mute witness to the fury and hate of Kor Megron, the Reaper of Rhodax.