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The Thieves' Guild in Cyrodiil was once the center of the Thieves' Guild in all of Tamriel. Ruled by the infamous Grey Fox, backed by the blessings of Nocturnal, and able to target any location in Cyrodiil, they were a force to be reckoned with.
In the 4th Era
By the time of the 4th Era, 201, the Thieves' Guild in Cyrodiil is practically unknown. They have no direct contacts or bases of operations in Bruma, no known members. The only evidence of their existence is their Shadowmarks left on some of the buildings.