I am stuck in the northwest part of the catacombs prison. I am trying to free Miroden Silverblade from his Cult captors. I am standing in front of a set of double metal doors on a south west wall. My thief can't pick the lock. It is requesting a black key. Anyone know where this key is? I'm aimlessly wandering here. I've opend all boxes and chests but can't find it.

I suppose you're looking for a Black Steel Key. That key can be get only from battle with Cult forces (they drop it on the ground after the battle). Are you sure you killed everyone and checked up everything that dropped on the ground?

I went and searced everywhere and couldn't find it. I assume I overlooked it when I killed the cult forces in question. I was forced to go back to a previous save game prior to entering the catacombs prison lelve. Strangely, when I finally got to the same door I didn't need a key this time. Anyway, thanks for the help.