Heretic was different precisely because it was not neither futuristic, nor contemporary. It's setting was a dark underground realm of fantasy, and the main character, Corvus, was a sorcerer that had to fight various monsters and evil creatures throughout multiple levels. The plot is a typical tale of the genre. Corvus — one of the Sidhe elves — has to fight against D'Sparil, one of the three Serpent Riders, and his armies of beast underworld creatures. The Serpent Riders had dominated and possessed all seven kings of Parthoris; Corvus, being an elf, is somewhat immune to the sorcery of their enemies. Nevertheless, he has to take severe countermeasures against the possessed kings, to diminish the malignity of its power and to fight heavily to reduce to ashes the evil dominance of D'Sparil and his horrible army of depraved creatures.
Despite the fact that heretic was a success, on the other hand, the game never really achieved the status it certainly deserves, for being the only one of its kind. Exceedingly wonderful to play, Heretic would be obscured, at least partially, by its most sucessfull sequel, Hexen: Beyond Heretic, which had a somewhat different storyline, although it shared explicitly the universe of dark fantasy of its predecessor. A more direct sequel — with a continuing premise — was released in 1998, as Heretic II.
Heretic was one of those games that people of my generation used to play in their youth, during the mid to late nineties. It certainly was a great game, that not only deserves to be properly remembered, but also introduced to the younger generations, that probably never heard anything about Heretic before. Undoubtedly a crucial first-person shooter game — envisioned in a sinister and nefarious world of dark fantasy and wizardry —, Heretic continues to this day to be one of the most marvelous representatives of interactive adventure, and an entertaining tale of spectacular density, in the history of computer games.