"I do this not for my glory, nor the glory of the Despoiler. I do this for the glory of the Black Legion, the Dark Gods and Chaos!"
- — Ygethmor the Deceiver
Ygethmor the Deceiver, known also as the "Twice Damned" and the "Purgator of Corrialis," is a formidable Sorcerer Lord of the Black Legion. He currently serves as one of Abaddon the Despoiler's lieutenants and a member of his personal retinue, the Chosen of Abaddon. Ygethmor is the current Lord Deceiver, whose visions of the Warp lead the Black Crusade from star system to star system. During the 13th Black Crusade in 999.M41, the Officio Assassinorum sanctioned the deployment of an assassin team to eliminate Ygethmor, amongst other notable targets in service to the Archenemy. Whilst scrutiny of their field records is impossible, at least seven Assassinorum agents are known to have failed in the attempt to take the life of the Deceiver.
Little is known of the personal history of the vile creature known as Ygethmor the Deceiver before he rose to prominence during the 13th Black Crusade in 999.M41. It can be assumed that he was once a Legionary who served within the ranks of Sons of Horus Legion during the Great Crusade and the terrible intergalactic conflict known as the Horus Heresy over ten thousand standard years ago. As a Chaos Sorcerer, he possesses powerful psychic abilities, which may hint at his origins as a former psychic servant of his Legion's Librarius. During the early years of the Great Crusade, many Astartes of the Space Marine Legions began to display powerful psychic abilities. At the urging of the powerful psyker and Primarch of the psychically-gifted Thousand Sons Legion, Magnus the Red, as well as some of his fellow Primarchs, this led to the creation of the Librarius within each Legion, whose psychically gifted Battle-Brothers would seek the betterment of their Legion and the expansion of the burgeoning Imperium of Man. When Horus was corrupted by the powers of the Chaos Gods and began the internecine conflict known as the Horus Heresy, the Librarians of those Traitor Legions that followed him spat upon their oaths of fealty to the Emperor and dedicated themselves to Chaos, receiving new psychic powers. The only exception were the Librarians of the World Eaters, who were hunted down and slain by their brethren as a bloody sacrifice to Khorne, for the Chaos God of war and murder hates all practitioners of sorcery, which he sees as dishonourable trickery when compared to the joys of simple, blood-drenched slaughter.
13th Black Crusade
In 999.M41, Abaddon launched his 13th Black Crusade, which resulted in the largest mobilisation of both Imperial and Chaotic forces seen in the Milky Way Galaxy since the Horus Heresy. Though Abaddon's attempt to break through the Cadian Gate into open Imperial space proved ultimately unsuccessful, the advances made by his forces have gained him much more than was initially realised. His retinue of Chosen, led by Devram Korda, the "Tyrant of Sarora," returned to his side in the closing days of the war, bringing with them two individuals who had journeyed to the centre of the Eye of Terror. Together with Ygethmor the Deceiver, they presented Abaddon with the Heart of Chaos, a powerful Chaos artefact that Zaraphiston, the Chaos Sorcerer who served as one of Abaddon's Chosen, and a long-time hated rival of Ygethmor, had claimed could not exist. It is known that Ygethmor now stands at Abaddon's right hand as his Lord Deceiver, while Zaraphiston's status remains a mystery. What this object is or its true abilities are, no one knows, but it definitely bodes ill for the Imperium.
The Fall of Medusa V
Ygethmor was later gifted a vision by the Warp, a glimpse of a future that might be. He saw himself exalted upon a mountain of corpses as the undiluted power of the Empyrean writhed about him. He saw a planet scoured by the power of Chaos, transmuted into a Daemon World and himself as its master. To achieve his aims, Ygethmor gathered about him a mighty force, a conglomeration of Chaos Space Marine warbands, each of which was an army in its own right, and each led by a Chaos Lord hungry to share in the glory. Fulgrim's Champion, Lucius the Eternal, stood ready to fight beside Ygethmor's warriors, and two Great Companies of Iron Warriors readied their wargear to support the Deceiver. The Dark Apostles of the Word Bearers roused the masses against the False Emperor and the Alpha Legion's spies stirred rebellion in the great hive cities throughout the sector. Renegades from within the Maelstrom flocked to the cause as well. Even Ignatius Grulgor, beloved of Nurgle, and a warhost of Death Guard under his command stood ready to go to war at the Black Legion's side. Abaddon granted the Chaos Sorcerer four Black Legion companies, to be chosen by the Deceiver himself. Thousands of Chaos Space Marines from the Traitor Legions rallied to his cause, their numbers swollen by Renegade Space Marines from around the Imperium. Every warrior in Ygethmor's army fought to honour the Dark Gods and for the bounteous blessings of Chaos should they succeed.
Following the 13th Black Crusade's end, Ygethmor was responsible for the destruction of the population of the worlds of Corrialis and Galafonte. Ordo Hereticus agents in the Galafonte System failed to learn the lesson of what Ygethmor was capable of following the Corrialis Massacres. In almost identical circumstances to what had happened on Corrialis, the population of Galafonte turned upon itself, worshipping the Dark Gods of Chaos in a frenzied slaughter of all life in the heavily populated star system. The Inquisition later speculated that the extermination of both Corrialis and Galafonte were little more than "experiments" in damnation, paving the way for Ygethmor's attempt to transform himself into a Daemon Prince on Medusa V. Ygethmor commanded the powerful Repulsive-class Grand Cruiser Blade of Damnation, which boasted firepower and accuracy far above other vessels of its class. The Blade of Damnation was known to be possessed by a daemonic spirit, which was consistent with the many infernal war engines used by Ygethmor's Black Legion warband of Chaos Space Marines.
During the campaign later named the Fall of Medusa V by the Imperium, Ygethmor knew what must be done if he was to realise the future the Ruinous Powers had promised him -- the planet had to die. Atop a pillar of cadavers heaped upon the ruins of the Imperial Cathedral in the planet's capital city of Hive Euryales, a sorcerous ritual of inconceivable power had to be enacted. At the very moment that an approaching Warp Storm engulfed the planet, Ygethmor would be required to call upon the unlimited power of the Warp. Yet, for this ritual to succeed, it required millions of lives to be sacrificed to the Dark Gods and the glorious victory of the Forces of Chaos over the world's Imperial defenders. For Ygethmor, the prize was the power of the Warp unleashed and dominion over what might become his Daemon World of Medusa V. Despite his promises to Abaddon, Ygethmor fought for more than the glory of the Warmaster and Chaos; every victory brought him one step closer to daemonhood.
Ultimately, Ygethmor's plans to ascend to daemonhood were foiled; while many aspiring Chaos Champions were able to achieve battlefield glory during the campaign on Medusa V, they were unable to claim the planet for the Ruinous Powers due to the heroic resistance of the Imperial forces. Ygethmor was slain by the blade of the Eldar Autarch Elarique Swiftblade of Craftworld Alaitoc, and those Champions of the Dark Gods who had followed him were left to their fates on the dying world as the Warp consumed them.
- Apocalypse: Reload, pg. 55
- Codex: Chaos Space Marines (3rd Edition, 2nd Codex), pg. 10
- The Fall of Medusa V (Campaign Booklet), pp. 12, 16-17, 24, 26-27
- White Dwarf 287 (UK), "Eye of Terror Worldwide Event: Death by a Thousand Cuts," pg. 36