Oberdeii was a Scout of the Ultramarines' 199th 'Aegida' Company during the Horus Heresy. Still in training under Sergeant Arkus by the Shadow Crusade, he was stationed on Sotha where he experienced a prophetic vision of an impending disaster upon his world after venturing inside the Pharos. He was investigated by the Legion's Librarians for any Chaos taint, but despite his fears of rejection into the Ultramarines he was cleared.[1a] His visions, including the predicted arrival of the Blood Angels in Imperium Secundus and the Battle of Sotha, went unheeded.
After Arkus died early in the Night Lords attack on Sotha, Oberdeii led his scout squad to the surface of the planet, where they fought alongside the Auxilia of Mericus Giraldus.[1b] Oberdeii survived the battle, and upon debriefing with Roboute Guilliman was promoted to a Reconnaissance Squad Sergeant by the Primarch personally.[1c]
Oberdeii was later promoted to Captain of the Aegida Company, which was maintained by Guilliman's own will even after the Second Founding as a phantom 11th Company in defiance of the Codex Astartes. As Warden of the Pharos, he swore the 'Aegidan Oath' on the Gladius Incandor to protect Sotha from whatever secrets had been buried in the Pharos. The oath of moment, written by the primarch's hand, was kept within the Pharos with the skull-mask of Barabas Dantioch, first Warden of the Pharos.
By the time of the Third Founding, Oberdeii was the last surviving member of the Aegida Company. Seeking to remove evidence of Guilliman's defiance of his own Codex, Chapter Master Tigris Decon, sent Chaplain Segas to Sotha to offer Oberdeii a choice of reassignment to the 5th Company or continuing to guard the Pharos by becoming Master of a new 'Aegida Chapter'. Oberdeii, initially appalled that Rogal Dorn had initiated another founding, reluctantly agreed to found a new Chapter, but chose to name them the Scythes of the Emperor.
- Oberdeii's proclamation for the people of Sotha to "...turn their ploughshares into swords...", is a reversal of the concept of "swords to ploughshares", fitting for a grim darkness in which there is only war.
- 1: Pharos (Novel)
- 2: The Heart of the Pharos (Audio Drama)
- 3: The Aegidan Oath (Short Story)