The Ratway Warrens

The Ratway Warrens is located south of The Ratway Vaults. It seems to be a prison of some sort for the mentally challenged.

Two people here come up as hostiles. Hefid the Deaf is probably the first one you will come across. Upon opening the room she's in, she may run if you startle her. The second character, who is actually hostile, is Knjakr, a chef. Upon activating him, he will attack.

The other two people you will encounter down here is Salvianus, who seems to be an ex-imperial officer, judging from the items located near him. The last person you will find is Esbern (Skyrim). He is quite distinct in that he only talks from behind a door that the player may not have access to opening.

Note: After reading Hefid the Deaf's profile, it seems that the people down here are part of The Insane Clan.