The Puzzle Box

From the introduction: The PCs obtain a mysterious puzzle box only to become trapped in an extradimensional mansion within it. There, they meet Glowdrop, a creature of light working against the mansion's owner Lumestin, an artist able to craft objects from light itself. After getting caught up in deadly conflict between the artist's apprentices, the PCs must stop a darknessspewing contraption to get to Lumestin and find their way home. User summary: For 8th level characters.