A native of one of Calth's noble families, he was brought up in the principle arcology of Gallica Subdelta. As his family's estates were mostly in the vast underground networks of Calth, he did not see the light of day for the first ten years of his life. During this time he became known as Aethon the White Spider due to his masterful knowledge of Calth's underground labyrinths. He eventually was pressed into the Ultramarines, rising to the rank of Captain and aiding Roboute Guilliman himself in designing the world's defenses. During the Great Crusade, he fought alongside the Word Bearers against Orks, gaining a friendship with Kurtha Sedd.
When the Word Bearers betrayed his Legion, he took part in the Battle for Calth and later became a Praetor. During the battle he led the Ultramarines' forces beneath Calth's surface against the Word Bearers who still infested it, in what became known as the Underground War.