I've tried every piece of metal from the basement so far, and I haven't figured out how to actually get into level 11 yet either. I have the Steel Gear, the Bladed Gear, and the Ore. At least I am pretty sure that's what those three are called. I am using the original copy of Grimlock, not the update. I have found a few secrets on the 13th floor and none on the 12th floor yet. Also I haven't had a key to get into any of the rooms on the 12th floor.
I've been REALLY meticulous up to this point, so the fact that something this stupid is eluding me this close to the end of the game is upsetting, not to mention the fact that I feel like it might have bugged out.
Please help.
