Urkrathos, also sometimes called Urkanthos, was a Chaos Lord of the Black Legion of Chaos Space Marines and the Lord Purgator of the Chosen of Abaddon, as well as the master of his Black Fleet. Ironically, Urkrathos, who had become a Daemon Prince after pleasing his patron, the Blood God Khorne, was temporarily slain during the 13th Black Crusade on Cadia itself. He fell just before Cadia's destruction at the siege of Kasr Kraf combatting Saint Celestine and her two Geminae Superia, the Living Saint's protectors, the former Adepta Sororitas Canonesses Eleanor and Genevieve of the Order of Our Martyred Lady. Urkrathos had previously killed both in combat before their resurrection by the power of the Living Saint to serve as her eternal honour guard.
Within the ranks of the Black Legion are those who are bloody-handed servants of Khorne. Though not a single unified warband within the Black Legion, they are collectively known as the Hounds of Abaddon. Urkrathos, the current Lord Purgator and commander of the Legion's Black Fleet, claims all followers of Khorne within the Legion as his own and directs them according to the will of Abaddon the Despoiler, the Warmaster of Chaos and master of the Black Legion. It falls to the Lord Purgator to ensure that every man, woman and child left alive on a world conquered by the Black Legion is dragged in chains into the hold of the Legion's starships, and that no edifice remains undedicated to the Dark Gods.
During the final stage of the 13th Black Crusade in 999.M41, Urkrathos, preferring his alternate moniker Urkanthos, achieved daemonhood and became a Daemon Prince after pleasing Khorne with the mass slaughter and loss of life caused by the destruction of three great Imperial warships in the Cadian Gate. The ascension of Urkanthos to daemonhood came as the Black Fleet approached Cadia for its second assault upon the world. Surging in towards the Fortress World, Urkanthos had faced a trio of enemy Battleships whose captains had determined that -- if they could not defeat the oncoming Chaos horde -- they would at least slay the ﬂagship of its ﬂeetmaster. Through guile, ferocity and unmatched skill did Urkanthos captain his craft to victory over all three Imperial warships, blasting two to ruin before obliterating the final craft as it turned to ﬂee. Such a mighty tally of blood and skulls pleased Khorne greatly, and bought Urkanthos the reward of immortality that he had long sought. So did the master of the Hounds of Abaddon become more fearsome than ever before.
Once the Black Fleet arrived in orbit of Cadia, Urkanthos was given the honour of leading the Chaos assault upon the Fortress World's strongest knot of defenders -- led by Lord Castellan Ursarkar E. Creed himself -- at Kasr Kraf. But, just as it seemed Urkanthos and legions of daemons and Chaos Space Marines would at last carry the day in the name of the Despoiler and the Dark Gods, the Living Saint Celestine appeared swathed in flame above the bloody Cadian battlefields of Kasr Kraf. But she did not come alone, for she brought with her some five companies of Adepta Sororitas of the Order of Our Martyred Lady, thought lost in the Warp some fourteen hundred standard years before. Her radiant light had served as a beacon through the Empyrean, drawing the wounded vessel into the path of another Imperial craft and binding the two until realspace claimed them both once more.
With the Battle-Sisters' arrival, the battle for Cadia shifted for a time in the Imperial defenders' favour. Celestine immediately engaged Urkanthos near the Cadian fortresses' Egressium Gate, with two Canonesses of the Order of Our Martyred Lady he had already slain earlier during the battle for Kasr Kraf. Celestine had used her power and their extraordinary faith in the Emperor of Mankind to bring them back to life to serve as her eternal honour guard. These were Genevieve and Eleanor, the Living Saint's Geminae Superia.
Urkanthos lurched through the Egressium Gate, his wings scattering the ashen remains of what had once been men. The Despoiler's will had been done. Cadia would soon die, and Urkanthos had no desire to die with it. It was time to depart and claim his reward.
An Imperial Guardsman ran headlong towards the Daemon Prince, bayonet lowered. Urkanthos eviscerated the mortal with a single savage swipe. Licking blood from his talons, he let the body fall upon the remains of the black-clad prayer-witches who'd sought to bar his ingress.
Slaughter still raged across the muster field of the kasr, the tempo and scent of it somehow different. Urkanthos longed to join it, even though to do so was to risk annihilation beneath the Blackstone's gaze.
In a swoop of wings, Celestine landed before Urkanthos, her armour glittering in the golden light of her halo. At last, the Daemon Prince recognised the altered stench -- the battlefield stank of her faith, her certainty.
"The corpse-bride," he growled.
The angel raised her sword, the point steady as a rock. "Your hour is done, beast."
Urkanthos laughed, the sound of it a rough peal of thunder. "It has only just begun. You are nothing. The echo of a false god. I will break you in half and set your skull upon Khorne's throne."
Agony wracked the Daemon Prince, a white heat searing the veins of his chest. Through slitted eyes, he saw the corpse-bride regarding him, unmoving. The pain passed. As ever, Urkanthos felt the stronger for it. Another trial endured.
"I am the Scourgemaster of the Black Fleet, the Right Hand of the Despoiler. You cannot match me alone."
Urkanthos pressed a taloned hand to the site of the faded agony. Something was wrong. The sword in his ﬂesh -- the prayer-witch's sword -- had gone. He spun around. Two prayer-witches stared back, their faces alive with light, their golden armour as radiant as a sun. Urkanthos, who never forgot those he slew, knew their faces. The twins he'd killed upon the threshold of the Egressium Gate. His seething ichor dripped from the leftmost's blade. The blade so lately trapped in his ﬂesh. The first glimmer of uncertainty trickled into the Daemon Prince's bartered soul.
"I am not alone," said Celestine. "And your hour is done."
With a roar, Urkanthos swept back his wings, and pounced.
Together, the Living Saint and her reborn warriors slew the over-confident servant of the Dark Gods. When they threw the Daemon Prince's broken body from the walls of Kasr Kraf, it helped to demoralise the Despoiler's forces, routing them and buying the Imperials of Cadia some needed breathing space between constant Chaos assaults.
Though Urkanthos failed on Cadia and was banished back to the Realm of Chaos by his death in realspace, as a Daemon Prince, he was now an immortal being. The only certainty was that sooner or later, Urkanthos would be back to vex the servants of the Corpse Emperor...
- Black Legion: A Codex: Chaos Space Marines Supplement (Digital Edition), pp. 55-63
- Codex: Chaos Space Marines (3rd Edition, 2nd Codex), pg. 10
- Gathering Storm - Book One - Fall of Cadia (7th Edition), pp. 36-53