Oberdeii, known as the Warden of the Pharos, was the first Chapter Master of the Third Founding Scythes of the Emperor Space Marine Chapter. Originally a Scout Marine of the 199th "Aegida" Company of the Ultramarines Legion during the Horus Heresy, he would go on to be a part of the events surrounding the mysterious xenos artefact known as the Pharos on the Agri-world of Sotha during the dark days of the Heresy. Following the Battle of Sotha, he was promoted to Reconnaissance Squad Sergeant by Primarch Roboute Guilliman personally. He would later be promoted to Captain of the Aegida Company, which acted as a phantom 11th Company of the newly divided Ultramarines Chapter in defiance of the Codex Astartes on the orders of Guilliman himself. He would maintain his vigil over Sotha for centuries, until the dawning of the 32nd Millennium. During the Third Founding, he was offered the choice to be reassigned as a part of the Ultramarines Chapter's 5th Company or to continue his vigil as Chapter Master of a new "Aegida Chapter." Oberdeii reluctantly accepted the latter choice, and became the first Master of the newborn Chapter he renamed the "Scythes of the Emperor."
Oberdeii was a young Scout Marine who was originally a member of the Ultramarines Legion's 199th "Aegida" Company, which was assigned by the Primarch Roboute Guilliman to the world of Sotha as permanent protection. The assigned Astartes took pride in their duty and later adopted the crossed scythes symbol upon their pauldrons to symbolise those they protected, the scythe-wielding agriculturalists of Sotha. For over a standard century, the Astartes had carried out a ritual in which they cleared the area about the research site on Mount Pharos using a scythe. This simple rural tradition gave rise to the protection company's choice of icon.
Sotha was classified as a resticted world by the Ultramarines due to the fact it was home to a strange pre-Imperial biotechnological device known as the Pharos, which was located within the massive geographical landmark also called Mount Pharos. This strange alien device was built by an unknown xenos civilisation that harnessed the psychic energy of empathy to aid navigation through the Warp, much like the Astronomican, but on a much smaller scale. This device was utilised by Roboute Guilliman as a psychic beacon to attract Loyalist forces of the region that had been scattered by the Ruinstorm to the Ultramarines' homeworld of Macragge. Cut off from all travel to or communication with the Throneworld of Terra by that great Warp Storm conjured by the Word Bearers Traitor Legion during the Battle of Calth, Guilliman had created his own rump interstellar empire, the Imperium Secundus, to rally the Loyalist forces against the Traitors and maintain the ideals of the Emperor of Mankind.
Oberdeii was stationed on Sotha and was still in training under Sergeant Arkus when the Shadow Crusade -- the joint-campaign conducted by the World Eaters and Word Bearers Traitor Legions - had begun their campaign of terror against the worlds of Ultramar. While on Sotha, Oberdeii and another young Scout, named Tebecai, descended into the depths beneath Mount Pharos in search of the truth about the mysterious xenos artefact. Whilst in the bowels of the mighty and foreboding mountain, Oberdeii experienced a prophetic vision of an impending disaster upon Sotha. He was subsequently investigated by the Legion's Librarians for any sign of Chaos taint, but was subsequently cleared of corruption, despite his unfounded fears of rejection into the XIII Legion as a fully-fledged Battle-Brother. These prophetic visions included the imminent arrival of the Blood Angels Legion, which had recently returned from the Signus Campaign, and had followed the beacon of the Pharos to arrive in the newly created Imperium Secundus. Oberdeii also saw the impending disaster of the internecine conflict that would come to be known as the Battle of Sotha -- a massive conflict between the Ultramarine defenders of Sotha and a large Night Lords Traitor Legion contingent. But Oberdeii's warnings went unheeded.
The Pharos later became a source of contention between the Loyalists and Traitors when members of a Night Lords Traitor Legion splinter fleet under the command of Captain Krukesh the Pale sought to claim it from the forces of the Imperium Secundus during the Battle of Sotha foreseen by Oberdeii. During the Battle of Sotha, the Loyalist Iron Warriors Warsmith Barabas Dantioch sacrificed his own life to overload the Pharos, disabling the Night Lords fleet above Sotha and allowing the Loyalist forces to prevail.
After the Horus Heresy ended, and the subsequent Second Founding occurred in 021.M31, the Space Marine Legions were sundered into smaller separate formations known as Chapters in accordance with Guilliman's Codex Astartes. Oberdeii was later promoted to become Captain of the "Aegida" Company, which was maintained as a phantom Eleventh Company on Sotha, even as Guilliman forced every other Chapter to conform to the Codex model of maintaining only ten. Quite aside from the secret shame of the Imperium Secundus, the existence of the Aegida Company could have been seen as proof of the Primarch's wilful and deliberate flouting of Imperial decree -- a decree that he and his surviving loyal brothers had agreed upon only after much conflict.
Oberdeii was a living breathing reminder of what the Ultramarines considered in their vanity to be Lord Guilliman's mistakes. They could not erase them from the pages of history while Oberdeii remained on Sotha, oathed to the final duty that he had been given by the Primarch. As "Warden of the Pharos," Oberdeii swore an Oath of Moment, known as the "Aegidan Oath" on Guilliman's blade Gladius Incandor to protect Sotha's secrets buried in the Pharos. This Oath of Moment, written in the Primarch's own hand, was kept within Mount Pharos along with the skull-like iron mask of the fallen Barabas Dantioch, the first Warden of the Pharos.
By the time the Imperial Fists Primarch Rogal Dorn initiated the Third Founding in 001.M32, Oberdeii was the last surviving member of the Aegida Company. He was not simply the reminder of a mistake -- he was the embodiment of it. The time had come for the Aegida itself to be purged. In order to remove any evidence of perceived heresy on the part of Guilliman, as well as his complicity in defying the Codex Astares, Ultramarines Chapter Master Tigris Decon sent a representative, Chaplain Segas, to Sotha, to offer Oberdeii a choice of reassignment to the Chapter's 5th Company or to continue his watch over the Pharos by becoming the first Master of a new "Aegida Chapter." Oberdeii was initially appalled by the fact that Rogal Dorn would initiate yet another Founding, but reluctantly consented to becoming the Chapter Master of a new Chapter, and instead chose to name this new force the "Scythes of the Emperor." To populate the new Chapter Chaplain Segas and Brother Wenlocke -- along with seventy-two Ultramarines Veterans of the Orlan Conquest -- were assigned to become the first Scythes of the Emperor. The Scythes established a fortress-monastery upon their Chapter homeworld of Sotha. From this base of operations, near the region of space known as the Damocles Gulf in the Segmentum Ultima, the Chapter took upon itself the duty of policing and safeguarding many of the nearby mining and manufactoria settlements.
- Pharos (Novel) by Guy Haley
- The Heart of the Pharos (Audio Drama) by Laurie J. Goulding
- The Aegidan Oath (Short Story) by Laurie J. Goulding