The Plague Legion is a military force created by Lars Landred that is completely composed of undead soldiers. Their only purpose is to serve and carry out the will of their master all in the name of the Plague Empire.
After Lars' physical body was destroyed at the hands of Guy Elron, his soul was then imprisoned within the Black Plague for a millennium until he could create a physical body again with the remnants of his armor.
With the bodies of the enemies he slew, he raised an undead army loyal only to him and continued his quest to unite all of Garweeze and the surrounding galaxy under the rule of his new empire.
Pawns - Foot soldiers that are used as "cannon fodder" most of the time.
Marksmen - Rangers skilled in the art of long ranged combat.
Reavers - (pictured above) Undead SwordSages usually used against powerful foes as well as the personal guard of Lars Landred.
Dark Bishops - Liches who have been defeated and then brainwashed into the service of the Legion.