A tower built to the moon is a cool, fairy-tale-feeling premise (even with the portal to make it fit the kind of setting we're working with here better). The lack of clear "good guys" also makes this an interesting one and very fitting in the Appendix N. There are two pretty big threats here with the giant and rime walker (I'm not super familiar with Shadowdark, but that's what I picked up). There's a lot for the party to sneak and dodge their way around on this tower.