Sadly, by the time I started getting into Dungeon Crawl Classics, the Purple Planet books were already on their way out of print, so I wasn’t able to get the boxed set or separate adventures. Here’s hoping they’ll release a hardcover reprint like The Chained Coffin. I mention this because I had no idea until I started reading Neon Knights that it was connected to the Purple Planet setting and that’s something a purchaser might want to know. It’s not necessary that you own the other to understand the adventure in general, but it’s clear that there are some references to factions and such from those other books that are not clarified here.
There’s a lot of potential in this scenario, though I think it would be best broken apart, expanded, and re-woven into an ongoing game. It deals with dimension/world hopping, with the PCs being plucked out of their own reality for a time, dropped back in, and plucked out again. I think this could be a really interesting curveball to throw at your players, but would be more effective if it were to happen over a long period of time. So, once every two to four adventures you might yank them out of whatever they’re doing and plunk them down in Vazhalo’s lair. This might also give you the opportunity to sprinkle in more clues in their own world about how to deal with things. Perhaps they meet more people with glowing pink eyes.
If you’ve got the Purple Planet stuff, you could use this adventure as a way to take your PCs to that world. If not, you could easily place Vazhalo’s place somewhere else. I think it’s probably important that it be located in a hostile desert, but where that desert is isn’t so important. I might completely drop the set-up of having the city the PCs begin at under siege. Instead, I think I’d just pull them out of other adventures or perhaps while in transit between locations, without preamble.
I suppose, if you’re in the mind to do it, you could run this scenario straight, though I think it would be kind of tough. Maybe it would work in a convention setting if you can keep things moving quickly and not let PCs get off track. That’s definitely not how I’m going to use it. I’ll be carving it up and using the pieces.