Sergeant Remas was the leader of the Scythes of the Emperor Space Marine squad which tried to apprehend the first Hive Ship which approached Sotha, prior to the planet's destruction by Hive Fleet Kraken.
After inserting by Boarding Torpedo, they ventured into the ship but were attacked by Tyranid creatures. Most of his squad was killed (including a warrior named Brother Harvan) and eventually only Remas and one other, Brother Tobias, escaped after crippling the ship.
Remas and Tobias drifted on their own ship until it was recovered by the Ultramarines. By that time, Sotha had fallen to the xenos invasion and was already a dead world. When he was discovered, the unconscious Remas was gripping tightly on to a tattered Chapter banner, which depicted the golden horseman symbol of the Scythes of the Emperor.
After he had recovered sufficiently, his rescuers took Remas to meet with Chaplain Cassius. The sergeant was dressed in a black tunic decorated in gold, rather than his power armour or other battle gear. His testimony that day helped Cassius in the organisation of the Tyrannic War Veterans.
Remas was relatively short for Space Marine, but solidly built. He wore three service studs in his brow, each inscribed with a small image of a horseman. He had the shadow of a deep, ragged scar across his left cheek, most likely a result of injuries sustained on the Hive Ship.