The Lost Island
The Lost Island alternates between being in the Astral Plain and the Physical World. It is mostly populated by Githyanki pirates. There is also an ancient temple on the island that is the home of an ancient black dragon and it's (now murdered by the party) child. The party finds The Whip of Binding here. Bucky is from the Lost Island.
The Lost Island is where Junpei Iori gets his memories back and leaves the party to fight cannibals.