Mysterious Key

The Mysterious Key is a hyper-rare drop from any enemy.

It is the key to the Mysterious Chest, a structure in the Dark Forest behind the Animated Armour's tower.

When the key is not in the players inventory and they try to open the chest, it will just say "locked" in the select menu. With the key in the inventory, the option to unlock the chest is visible. When unlocked, the chest will open and on the tile in front of it will drop a Morph Ring.