The Ruins of Woebrook (a.k.a., Fane of the Frost God)

From publisher blurb: In the Time Before, Willowbrook Mall was a hustling, bustling mecca of conspicuous consumption. But now, nestled deep in the deadly Hugeston swamps, sits the forlorn “Woebrook”: an overgrown, waterlogged, abandoned ruin. Well, maybe not all that abandoned... “The Ruins of Woebrook” is a post-apocalyptic adventure suitable for the Mutant Future retroclone of Gamma World and can be used as-is with it and any other sci-fi, fantasy, or post-apocalyptic games that use the "Basic" version of the OGL system, and easily adapted to other games using the same core rules.