Thank you! I think I may have finally gotten the UI and other features tightened up pretty good. :D
To get the key you will need to find and defeat Hrotsvitha. She can be found in the last area of the Cathedral archives (library), just beyond a door with no handle. The door must be burned by casting the Kenaz (fire) rune in front of it, OR by throwing the lantern offhand weapon at it (chance to get the lantern by defeating the Chariot boss).