Occultus

Occultus (隠された, Kakusareta) is a secret country that is half the size of the kingdom Fiore. It was founded over 400 years ago and now serves has a home for demons of all kind. It was formed by the Etherious, demons created by the Black Mage Zeref on the goal of forming a place for demons to live away from the hatred of the other races. The ruling body is a group of selected powerful Etherious known as the Thirteen Demon Lords.

Trivia
Occultus is Latin for Hidden, which matches the purpose of the country, to hide demons from the other races that would seek to destroy them.