Galuna Island

Galuna Island aka "The Demon Isle" is an island shaped like a cresent moon that is the home of friendly demons.

History
At onepoint they were under a spell that made them turn into humans in the daytime. The spell also affected their memory so they didn't remember they were demons, thus, they thought they were cursed to be demons at night. This led them to believe that the moon was the cause of their curse and thus they sought help from guilds to cure them.