The Twin Islands were two islands very close together in the Western Sea. They were used in a ruse by Vilu Daskar, who sailed the Goreleech to one end of the islands. When the Sayna came through the channel between the islands, the Goreleech stuck her with its spike "like a gnat on a pin", to quote Parug. Apperently, this ruse had been used many times before by Daskar, as he stated that "they always" come through the channel between the islands. Dangerous flesh-eating slugs appear to be the only inhabitants of the islands.
The Twin Islands appear in The Legend of Luke.