Read on hardcoregaming101.net:
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You'll probably never reach the end though, at least not without cheating and hex editing the game for infinite health (ironically the only way most US gamers ever saw the boss was through the cover art). For you see, Working Designs made a mistake when tweaking the parameters. As Vic explained on NeoGAF: "On Exile 2 it was an issue of limited number of modifications because we weren't doing the game reprogramming, Telenet was. It was a small number of tries. And on the second-to last time, we had it *almost* right, so we added like +1 to the monsters, but it was like that scene with the fat guy in Meaning of Life where the waiter gives him that one wafer and he explodes. That +1 exceeded some limit internally and made the monsters exponentially harder rather than incrementally. Since it was our last "fix" and we had production discs, I thought we were screwed and had made an unwinnable game. Fortunately, with some time and special strategies, we found out you could finish it. We made one of the hardest games ever - by accident."
Vic also gave some tips: "The biggest one is not to try to assault the worst monsters. Just let them hit you in the back, which will throw you backwards (which is really forward since your back is turned). It's an easy way to clear impossible rooms with those dragons that shoot lightning."
How unfortunate this mistake was, is debatable. Wicked Phenomenon is a good but not great game, and importing the Japanese version for its easier difficulty won't result in you missing any important dialogue (though you'll miss some of WD's visual improvements). The US version is also crazy expensive on auction, whereas Japanese online stores are selling their version for well under 1,000 Yen. That's like $10."