The Unlidded Eye, sometimes also called Inquisitors, is an organisation within Stygia, empowered by Charon himself and tasked with the protection of the Dark Kingdom of Iron. It answers only to Charon himself, and even the Deathlords have a healthy respect of them. They investigate threats against Stygia and specifically hunt renegades and heretics.
A member of the Unlidded Eye carries the authority of the Stygian Emperor and stands above even the Hierarchy and their Anacreons. They have the authority to soulforge everyone they deem to be a threat to the Empire (this is the "gentle" way they handle potential enemies) or to even free a Thrall. A member of the Unlidden Eye is normally immune against Stygian law.
Induction into the Unlidden Eye is a very dangerous thing. Any wraith in a Legion can be recruited. Some say that even Renegades and Heretics had been recruited. During their training, the aspirants learn some of the more powerful Arcanoi, visit other Dark Kingdoms, and sometimes even step down into the Labyrinth.
Even today, the Eye awaits the return of its master and follows the rules he laid upon his Empire and punishes those who disregard them.