- It can be found in the Nightmare of Mensis, in Micolash, Host of the Nightmare‘s boss fight arena. In the area for the second part of the boss fight, Micolash will eventually run into a large room with several enemies. He will sprint into a mirror at the end of the room and teleport away. The key is next to the mirror he jumps into.
The Iron Door Key is used to open a door in the boss arena with Micolash, Host of the Nightmare. The door is located in the wall to the left of the Hunter upon entering the area where you fight Micolash.
- It can be acquired during or after the fight with Micolash.
- The key has an "eye" on its handle that is similar to the Insight symbol that players have on their HUD. It makes sense that it does have that symbol, seeing as where it actually leads players to.