Grimrock

Completed the game today and defeated the , but one thing that kept annoying me through the later part of my game was the 1 extra iron key I had in my backpack.

What's it for? I think I recall being somewhere in a dungeon where I collected two iron keys, but only ended up using one. My guess is the other has use in the same area, but I can't remember where that was.

One iron key goes to the "Shortcut" in the sewers and that key comes from the pit-puzzle above.