Bent

First you will need to obtain the black key from the iron-bound chest east of the enchanter Cymeneth. To unlock this chest you will need to get the iron key from Focault himself. (This chest is also the one that can repop with the heart-shaped amulet.) Once you have the black key from the iron-bound chest go back two rooms west to the Narrow Corridor.

1S, 2E
Search to reveal a north exit.
2N, 2E, Down, 1W, 2Up, 1S, 2E, 2N
Unlock the north door.

Prepare yourself for CPK combat if you choose/need to and move north into the Vault where you should find Bent. (*Note, that he's not particularly hard to kill.) You can unlock and open a chest in this room which has the flag hide-long-descr so you won't actually see it in the room. The magic lock scroll can repop inside this chest, and also on Bent himself. (If you decide to linger so that you can repeatedly kill Bent for magic lock scrolls, the Vault is no-quit, no-recall, and you can't dig in the room so a black moonstone and/or featureless white cube will not help you get out of the room. The only ways out are to either unlock the door south and leave that way or to void out and you will appear back at the recall room, a Shadowy Entrance Hall. As a final note, the black key that unlocks the Vault door and the chest in the vault has only about 6 uses so you may want to keep track of how many times you use the key if you do choose to spend time in the Vault and don't want to have to void out in order to leave.)