Born on Delta Prime into nobility, his father was a steward to an estate on Bakka and Rath joined the naval cadets at Karmon College at the age of 14. He proved adept at dueling and surviving the rigors of naval life, commissioned as a Lieutenant on the Cruiser Diomedes. Later, he was promoted to a Damage Control Officer in the Battleship Word of the Emperor and earned great respect for his organizational skills. However it was as a Tactical Officer for the 34th Destroyer flotilla that Rath's strategic genius began to show. In a series of brilliant maneuvers with his swift gunboats, he defeated a fleet of Eldar Corsairs at Ganzona Rift. The 34th became known as the Rift Marauders and Rath received high decorations for the feat. Eventually, he rose to the position of Battlefleet Bakka's supreme strategist and was promoted to Admiral by Lord Admiral Vannion, eventually replacing him as the Lord Commander of Segmentum Tempestus.
Battle for Macragge
Commanding the Imperial Navy contingent charged with helping the Ultramarines against Hive Fleet Behemoth in the Battle for Macragge, Lord Admiral Rath personally led the effort in the Emperor Class Battleship Dominus Astra. During the space battle for Macragge when all seemed lost in the face of overwhelming swarms of Tyranid Bio-ships, Rath rammed the Dominus Astra into the center of the Tyranid fleet and detonated the ship's Warp Drives, sucking both the Tyranids and his own ship into oblivion.