Details unknown. Eye witnesses mention red eyes and crimson armor, the latter is believed to be a organic exo skeleton rather than military equipment.
Extremely little information exists of the Scourge, such as their real name. First encountered by Red Corsair pirates in 2381 during a scouting mission for Dirathian relics and other treasures the name 'Scourge' was coined by one of the surviving members talking about biological weapons and insects who turned "thirty hardened pirates into thirty people feeling the instant effects of hundreds of nasty diseases at once".
Wether or not there's any truth to this has been debated. As it currently stands most people believe that the Scourge is simply an elaborate plan for Red Corsair pirates to lure more people into uncharted space at the edge of the galaxy.
A single, blurry, holopicture exists of a Scourge soldier, standing guard in a swamp on a remote unnamed world. The explored who snapped the picture before rushing back to his ship mentioned "swarms of deadly insects surrounding the soldier". He later died from an unknown disease.