Castanamir's Island is a small, desolate island situated not far from the shore of a sea east of Evenhold, once the home of a mage known as Castanamir. Two hundred years ago Castanamir and his island both disappeared without a trace, but it recently reappeared and was investigated by the adventurer. Castanamir's underground dwelling is a complex set of rooms magically connected in unintuitive ways.
The island is the setting of Robert Davis's The Lost Isle, an adventure based on the AD&D module The Lost Island of Castanamir. Similarities in direction suggest that the island may be located in the Dreamless Sea.