Mainland is an island mentioned by various people, and is located in the Fourth Sea, both having not been added yet. According to the gun sellers and smugglers, guns originate from Mainland. It is supposed to be the biggest island in the game and one of the few islands that have undergone what is known as the "Iron Revolution", an advancement in modern technology.
- The music that would've been played at Mainland is "Road Hawgs - Brother".
- Mainland has been said to be twice as large as Alalea.