Mage Cube

From publisher blurb:

Mage Cube is a Fifth Edition plug-in adventure for four characters with an average party level (APL) of 5, 8, 11, or 14. This addon offers a general guideline on scaling the adventure for each level. A powerful mage has established himself and his apprentices in a non-Euclidean demiplane where he hides his most precious possession, a mysterious scroll. If the characters wish to abscond with this artifact, they need to contend with magical traps and summoned protectors.

You may also run this adventure as part of the Dungeon & Lairs Megamodule #2: Seekers of Yil. If you do, refer to the Seekers of Yil megamodule’s adventure hook, “The God of Secrets Appears,” to get your characters involved in the story.