Captain of the Doom Eagles Fourth Company from 544.M41 until his death in 861.M41, Diominus Feldon was a wise and thoughtful leader. Unlike many Space Marine commanders, Feldon valued the lives of his men and those of the other forces of the Imperium above personal glory, and even above his own life. For this among other reasons, Feldon was well-liked by his men, although the typical attitudes and culture of the Doom Eagles which Feldon embraced whole-heartedly prevented him from gaining much popularity outside of his chapter.
It was Feldon's dedication to saving lives that cost him his own life during the Desecration of Orphellion III in 861.M41. Feldon chose to aid the Aetherian Warriors Second Company when it was left for dead by Captain Fulvio Caro of the Aetherian Warriors Third Company. Surrounded by the enemy, Feldon was eventually cut down by Chosen Black Legionnaires. Feldon's protégé, Veteran Sergeant Egon Talorus, would then take up his Captain's hammer, the Fist of Raemnor, and used it to deliver righteous vengeance upon the Black Legion Champion leading the Chaos charge.
Feldon died without naming a successor, and while it is likely he would've chosen Talorus to lead the Fourth Company, instead the promotion defaulted to the Sergeant of the Company's Command Squad, Sedryk Hectorius.