Crater Island (also known as Boiler Island or Book Assembly Island) was the home of Gehn's office in Riven. It contained a large boiler (which contained a pipe that dumped it out to the sea) and had a large crater with a lake in the center. The island was home to a variety of cave frogs, which offers a clue to one of Riven's major puzzles. This article is a Stub. You can help D'ni by expanding it.