Continuity mistake: During the final battle between Boone and Decker, at one point, they are wrestling on a wooden bridge, and the board beneath Boone's head breaks in half and falls into the cavern below. (It is even highlighted in a very dramatic shot looking downwards over the whole cavern as it falls) Yet, a few shots later, the board has suddenly re-appeared beneath his head, unbroken.
Continuity mistake: During the final fight between Boone and Decker, right before he is killed, Decker almost falls backwards off a small "cliff", only to be caught by Boone. Watch the shots closely. In the first shot from above, he teeters on the edge, about to fall, and Boone isn't holding him. Yet in the next shot from below (looking upwards), Boone is holding onto Decker's shirt/jacket. The camera cuts back up above, and Boone is no longer holding Decker, but instead grabs him while shouting "Not yet!"
Revealing mistake: During the big final fight at Midian, at one point, one of the men with a flamethrower accidentally stumbles backwards into a patch of burning shrubs/plants, which sets him on fire and eventually causes his flamethrower tank to explode. As he accidentally stumbles back into the shrubs, watch closely- one of the plants starts to fall over, and is attached to a small square board hidden in the dirt below that becomes visible, revealing that the plants were pieces of set-dressing.
Trivia: Lylesberg, the "leader" of the Nightbreed, is portrayed by Doug Bradley. Bradley was famous for playing the character of "Pinhead" in most entries of the "Hellraiser" movies series, also created by Clive Barker. Several other minor characters in this film were also portrayed by other "Hellraiser" alum.
Trivia: In the original cut of the film, the character Narcisse (the man with the partially skinned head who Boone first meets in the hospital, then travels to Midian with after being resurrected) was killed by Decker during the final battle sequence. However, his character proved to be popular during early test-screenings, so his death was cut from the film, and director Clive Barker shot a few new scenes with the character to expand his role slightly.
Trivia: The post-production process of the film was very dramatic. The studios became worried that the subject matter was too strange for audiences, and in an attempt to make the film faster and simpler to understand, they demanded that nearly an hour of material be removed from the film. Director Clive Barker also maintains that the film wasn't marketed properly. A Director's Cut of the film (containing much of the cut footage) was announced more than 20 years after the film's original release-date.