Wardens Purgatory Post Banishment

"Nightmares are the epitome of Fear. Without them, galaxy is nothing more than a echo in the universe. We, are the harbingers of Nightmare, the lords of Fear. Rejoice brothers, for we are the heralds of fear, and the creators of Nightmare."
-Excerpt from The Nightmare Edict, Written by the Nightmare King before he and his Legion were banished.
The Wardens Purgatory are a Legion of Space Marines unlike any other. They were not ones that took part in the Horus Heresy, or one of the Legions who defended the walls of the Imperial Palace.