In , the Ultimate Key is one of the most important items to acquire. There are dozens of locked doors around the entire red, blue, and silver map.
The Thief's Key unlocks the red doors, the Magic Key unlocks the blue doors, and the Ultimate Key unlocks any and all doors.
I recommend finding the Ultimate Key as soon as possible, as many items and gear are locked behind doors. You must have acquired black pepper for the king of Portoga to receive his ship so you can sail the seas to find the Ultimate Key.
With their new gifted ship, you must now sail around the world to collect the orbs to wake the Everbird and face off against the boss Baramos.
However, unlike the previous two keys, finding the Ultimate Key is a multistep process that requires another important relic: the Bottomless Pot.