Where is Sigil?

Sigil, or the City of Doors, was the central planar hub of the universe. It contained gates and portals to anywhere one could desire to go from the Feywild to the halls of Valhalla. That was until it vanished from existence. This has confused scholars for thousands of years as, according to the very limited records that are stored The Grand Library of Unin, it one day just ceased to exist. No war, no upheaval, no great disaster, no survivors. All that is left of the once grand city are its towering walls and the barren waste that lays inside of them.

With planar travel becoming prevalent once again over the last hundred years due to the alliance between East and West Yuland and the formation of The Grey Cloaks, one might think that the ruins would have been thoroughly explored and researched. However, The Grey Cloaks avoid the area like a plague. They claim the ruins to be a cursed wasteland that no one should step foot on, lest they risk losing their mind to the great emptiness that is contained within its walls. The singular expedition ever to have been lead into the city returned with only half of the original members and those who returned had sworn an oath of secrecy among themselves to never talk about what had transpired there to anyone outside of the organization.

With their influence over the ruling class of East Yuland, the Grey Cloaks have managed to make travel to Sigil illegal for anyone outside the organization, thoroughly angering the scholars at Unin as, without information on the city, their records can never be complete. This lead the previous Speaker of Unin Seldanna Eljeon to steal the gate design to Sigil from the Grey Cloak's Citadel and travel there herself. Seldanna disappeared for months after crossing through the gate and most assumed that whatever the Grey Cloaks were avoiding in Sigil had killed her. When she did return, most of her skin had been flayed off and strange symbols marred whatever flesh still remained on her. The only information that the scholars of Unin were able to gain from her before Seldanna was apprehended by the Grey Cloaks was near incoherent babbling about a monolith in the center of the ruins and alien horrors wandering in the wastes.

Seldanna is still presumably under the custody of the Grey Cloaks and, due to the theft committed by her, sanctions have been placed over the library preventing any of the people who are studying there from accessing planar gates without written permission from a Grey Cloak.