Anah

 was a Janus living in a London trap street under the protection of Mayor Me and the mother of Anahson. Anah and Anahson had escaped slavery and sought asylum in the trap street. In the early 21st century, she was apparently murdered by Rigsy and stored in stasis. Me claimed she was being kept until someone came to bury her, even though the Janus cremated their dead. The Twelfth Doctor discovered that Anah was still alive, and found a key hole that needed the TARDIS key to release her.

This was in fact a trap orchestrated by Me to force a teleport bracelet onto the Doctor's wrist have him teleported (TV: Face the Raven) by Rassilon into the Doctor's confession dial for questioning, (TV: Hell Bent) as part of a deal Me made to protect the trap street. (TV: Face the Raven)