it's been awhile.... was the swamp after the desert and canyons? or before..
Anyways,, I think Drivaser (the next level) is the final one.

Uh- first was city, then underground, then ice, then desert/canyon and then swamp.
Great so only like 6-8 hours to go hahaha.

You can run through, skipping a few fights, until you hit a magic barrier. The last level is the city again but it is not as long.

You go from Soddentrod back to Drivasser, and that's the end.

I like the length as i feel i am getting bang for the buck . Especially as the levels are artfully created from scratch and not randomly generated .Consider it as just adding levels to your library because after you complete them once you can replay them at any time from a checkpoint if you particularly liked them or want to try a different strategy . This is one of the things that gives this game so much replay ability . After game + and you are a complete badarse mage you can go to any level and and have some fun with whatever lever demons or environments you want .