Terebinthia

Terebinthia is a sovereign island-kingdom in the Great Eastern Ocean, the closest island to it being the island of Galma, which is a duchy under the authority of the Kingdom of Narnia. In Voyage of The Dawn Treader, Caspian X claims that a sickness was going around and prevented them from landing

=Trivia= In Bridge to Terabithia the main characters create an imagenary world named Terabithia, the name Terabithia is likely derived from the name of this island.