The Legion is a mysterious order of demon-worshipers. While most of their rituals and practices are unknown, it has been stated that each member of the Legion is a highly skilled magic-user. How they have done this is debatable, but it is suspected to be due to some kind of outside tampering.
Members of the Legion are cold and ruthless, cutting down anyone that interfere with their goals. The Legion has stated their primary goal is to open a gate from Hell to Earth, unleashing the armies of Hell upon humanity. Additionally, the Legion uses a specially cursed type of blade, which makes it so that any injury inflicted by the blade cannot be healed.
The only way for the curse to be lifted is if an Angel and/or angelic being breaks the curse. There are several people curently on the run from the Legion: Annabel Fiala, Drake, and their two children, Skyler and Dante.