Revuel Arvida

Revuel Arvida was a 4th Fellowship Sergeant of the Thousand Sons Legion and a member of the Corvidae Cult during the Great Crusade and the opening days of the Horus Heresy in the late 30th and early 31st Millennium. 4th Fellowship Captain Menes Kalliston led a squad of Battle-Brothers to the ravaged surface of their homeworld to seek for any signs of survivors or their Primarch. Instead, their squad was taken by surprise when they encountered a much larger force of Traitor World Eaters who were also on Prospero for their own nefarious reasons. In the ensuing conflagration, the majority of the squad were killed and their captain was captured. Utilising his innate precognitive psychic abilities, Sergeant Arvida was able to elude the World Eaters and eventually escape the surface of the Dead World. Though his ultimate fate is unknown, Imperial scholars suggest that there may be some connection between Sergeant Arvida and the Blood Ravens Space Marines Chapter.

History
Throughout the Great Crusade, the psychically gifted Astartes of the Thousand Sons proved useful innumerable times as the XV Legion fought bravely in multiple campaigns, leaving few in doubt of their achievements. However, there were those Primarchs such as Leman Russ of the Space Wolves, Mortarion of the Death Guard and Corvus Corax of the Raven Guard who could never bring themselves to fully trust Magnus the Red and his Thousand Sons because of their own strong feelings against the use of sorcery and psykers in general. Magnus saw the potential in exploiting the powers of psychically talented Astartes and was instrumental in the development of the Space Marines' corps of Librarians. The Librarians quickly proved to be loyal and effective warriors and soon acceptance by the Emperor and the Primarchs for their presence on the battlefield. Librarians soon became a powerful addition to the ranks of the Space Marine Legions.

Librarius
However, there were those Primarchs who raised their voices in dissent, arguing amongst themselves and with the Emperor that Librarians should not be permitted within the ranks of the Astartes. Some desired to expand their Legions' Librarius and recruit even more Librarians into their ranks, whilst other Primarchs vehemently opposed the entire notion of Librarians and felt that they should be expunged from their ranks altogether. Dismayed at the accusations leveled against Magnus and the friction the issue was causing amongst his Primarchs, the Emperor was also concerned about the Librarians and the dangers they presented to the Great Crusade when he was no longer fighting directly alongside his Space Marine Legions. Before departing for Terra to begin his secret Imperial Webway Project within the seclusion of the Imperial Palace's dungeons, he summoned the Primarchs and all the other major Imperial leaders to a War Council summit on the world of Nikaea to address the Librarian crisis.

Council of Nikaea
To solve this growing dispute over the use of psychic abilities once and for all, the Emperor summoned the Imperial War Council to the newly terraformed Frontier World of Nikaea to resolve the issue over the use of psychic powers in the Imperium of Man and so Magnus could rebut the charges of sorcery that had been laid against him. This great conclave, later known to Imperial savants as the Council of Nikaea, consisted of the Primarchs as well as Imperial officials drawn from all the various Adepta of the Imperium. The Emperor's judgement at the Council of Nikaea proved severe. With the exceptions of Navigators and Astropaths who were properly trained, controlled and sanctioned by the Imperium and were necessary to its continued existence, the Space Marine Legions were no longer to employ psykers within their ranks. The Emperor commanded that the Primarchs were to close their Librarius departments forthwith and not to indulge the undoubted psychic talents of those Asartes who possessed the gift. All existing Space Marine Librarians were likewise forbidden to make use of their abilities. The Council's rulings also created a new position amongst the Space Marine Legions, the Space Marine Chaplain, to uphold the Imperial Truth and help maintain the purity of an Astartes Legion's dedication and fidelity to the Emperor's commands.

Furthermore, Magnus was ordered to return to Prospero to reorganise his Legion, disband the Legion’s Librarius and redeploy its existing large corps of Librarians to the Legion's Battle Companies. The Emperor censured his use of psychics and dismissed Magnus with a final threat -- a fate that had also befallen the Lost Primarchs of the II and XI Legions: "If you treat with the Warp, Magnus, I shall visit destruction upon you. And your Legion's name will be struck from the Imperial records for all time."

Scouring of Prospero
Bitterly disappointed by the outcome of the Council of Nikaea, Magnus secretly raged against the Emperor and what he saw as his father's unjust ruling. Yet Magnus had no intention of giving up the promised power and knowledge of the Warp and continued to study the Immaterium and its secrets. He met with his senior Librarians and persuaded them to collude with his plan to secretly continue their studies of the occult and sorcery in secret. Following the Council of Nikaea, a recall order was astropathically transmitted to all of the Legion's far-flung Expeditionary Fleets, with the bulk of the Legion's number present on Prospero just before the Fall of Prospero. However, some of the Thousand Sons' Astartes had not arrived on Prospero when that world was assaulted. This would include those elements of the Thousand Sons such as Captain Menes Kalliston and his 4th Fellowship. The fate of these Thousand Sons Astartes untainted by their Legion's fall to Chaos remains unrecorded -- or deliberately excised -- from Imperial records.

The Warmaster Horus was being treated for the mortal wound he had sustained fighting alongside his Luna Wolves Legion against the Renegade Imperial Planetary Governor Eugen Temba on the Feral World of Davin within the Temple of the Serpent Lodge. Unbeknownst to anyone else in his Legion, the Warmaster's healing had been prearranged by First Chaplain Erebus of the Word Bearers so that the Chaos Cultists of the Serpent Lodge could transport Horus' soul into the Warp where he was seduced by the Ruinous Powers into betraying and challenging the Emperor for control of the galaxy. Magnus, meditating on Prospero, peered into the Warp with his one good eye and foresaw the pact with Chaos that the dying Warmaster had made to save his life. He also foresaw the epic events that were yet to unfold in the galaxy and could prove dire to the survival of the Imperium.

Burdened with the terrible information provided by this precognitive vision, Magnus gathered about him the secret cabal of his Legion's Sorcerer Librarians to discuss and interpret the meaning and implications of these dire portents. Troubled by the revelations of Horus' betrayal and the coming galactic civil war, Magnus risked further censure from his father by employing the use of a daemonic spell to warn the Emperor. Magnus' spell breached the protective wards and hexes around the Imperial Palace and penetrated into the subterranean levels of the Palace's dungeon deep within the earth. Enraged by his son's breach of his edicts, the Emperor promised swift and unrelenting retribution against the Thousand Sons Legion. He unleashed his executioners -- the Space Wolves Legion, upon the sons of Magnus.

Return to Prospero
Six months after the tragic events of the Fall of Prospero the sanctioned Imperial military reprisal against the Thousand Sons Legion's homeworld of Prospero, Captain Menes Kalliston of the 4th Fellowship led a squad of Battle-Brothers to the ravaged surface of their homeworld to seek for any signs of survivors or their Primarch. Instead, this squad was taken by surprise when they encountered a much larger force of Traitor World Eaters who were also on Prospero for their own nefarious reasons. In the ensuing conflagration, the majority of the squad were killed and their captain was captured. Like all members of the Corvidae Cult, Arvida was skilled in the psychic discipline of precognition and the determination of the likely probabilities of future events. Despite his bleak circumstances as a captive of the World Eaters, Arvida knew -- as only a Corvidae could be certain -- that death would not find him on Prospero. That was no consolation for all that had been lost, but at least it lent the task of planning his next move a certain urgency. He would survive and live to discover the true causes of his Legion's destruction, and live to fight them. He would neither pause nor stumble until everything had been revealed to him, everything that would give him a weapon to employ. He is quoted as saying "knowledge is power," suggesting another connection between the Thousand Sons and the Blood Ravens Space Marines Chapter. Ironically, the symbol of the Corvidae Cult is that of a black raven's head. It is generally assumed that Sergeant ARvida somehow evaded his pursuers and managed to escape the surface of Prospero, but as to his ultimate fate, it currently remains unknown.