This is an adventure that perfectly captures the science-fantasy spirit of Appendix N, feeling like a story straight from Leigh Brackett. The writing is clear and evocative, establishing a great central mystery with the doppelgänger wizards, Malundro and Ordnulam. The layout is clean and highly usable; the pointcrawl map of Umbriel is easy to read, and all the necessary information is presented clearly. The art is also effective, adding to the module's old-school, astronomical feel. Bravo!