Sanctum of the Teesh

This secret complex under the Hall of Records is the realm of The Teesh. Many of the Teesh nearly never leave these underground walls where they toil for only one goal -- to divine the needs of The Lady of Pain and follow her will.
The underground complex is not massive, but it is roomy enough to hold its 100 or so members relatively comfortably. There are no windows and no fresh air, but this is Sigil - The City of Doors -- The Bird Cage -- they don't really feel like they are missing much.
Iateesh Glavin  is the current leader of the Teesh -- a position he has held for about 90 years.
The Sanctum contains all of the things you would expect of a secret underground sub-faction hideout. There is a large kitchen, a dining hall, dormitories for up to 100 people (it is currently very full since Glavin had warning that The Kateesh was on hand). It contains a training area with a battle master and a small library with a wizard trainer. There is a small shrine to Kord that is used mostly by Glavin.
There was a permanent portal to The Heroic Domains of Ysgard here. It was through there that most of the secret comings and goings, and also most of the import of supplies and export of refuse, was done by the Teesh. Unfortunnately this door, like all the others of Sigil, is currently slammed shut. The lack of access to the out plane will quickly stress the sect members and strain their resources.
But there are a few secret exits out of the sanctum that don't involve the Ysgard portal. One exit leaves through a concealed door in the side of the Hall of Records. The Teesh do not like to use this concealed door except in extreme emergency as it is thought that it would too easy to be caught. However, it is through this door that the Kateesh is brought in Act 2: Information from Glavin. Hamil Seggern was so excited to have found the Kateesh that he may not have made the best decision as to bring them in this way in moderately well-lit hours.
The Sanctum is also connected to a few of the nearby homes via undergound passages. One of these has been prepared as the base of operations of the Kateesh . It is stocked with food, drink, and nearly any other mundane and cheap thing a character could want.