- Badass Decay: A bit of a tossup. In the novel Glaeken murders a boat captain who betrays him and also kills two Romanian soldiers, but doesn't fight back against the Einsatzkommando and gets taken out rather easily. In the film, the captain never betrays him and he merely bullies his way past the Romanians, but the movie makes up for this by letting him openly resist the Einsatzkommando and even kill one of them.
- Complete Monster:
- Radu Molasar, the ancient, demonic force sealed within the Keep, introduces itself by murdering the tomb raiders that discover it, going on to devour the life from countless German soldiers in the area and driving the local villagers slowly insane with its presence. Vying for its freedom to walk among the Earth again, Radu Molasar manipulates a Jewish professor named Theodore Cuza by pretending to be a guardian for the Jewish people, restoring his body and stringing him along for his own ends. Radu Molasar kills the SS leader Kaempffer and his entire garrison, and, when Cuza denies him his freedom upon seeing it for the monster it is, Radu Molasar returns him to his crippled body out of spite and attempts to murder both him and his daughter for their defiance.
- SD Sturmbannführer Erich Kaempffer is a brutal Nazi enforcer dispatched to investigate the Keep in response to the German deaths. Kaempffer introduces himself having three of the local villagers executed to curb "partisan" activity, ordering his men to execute more for each German death until they run out of villagers to kill. Giving free rein to his men to abuse the villagers and threatening to torture those who do not comply, Kaempffer ensures the compliance of Cuza when he's brought in to translate the Keep's message by threatening to have him and his daughter sent to the camps. A craven bully at heart, Kaempffer guns down his own associate Woermann to steal his cross, shortly before he is killed by the malignant force he himself is little different from.
- Cult Classic: Despite going through terrible series of Executive Meddling, which turned the plot into incomprehensible mess, along with bombing hard in cinemas and being burried by Paramount to pretend it never happend, the film still gained a very strong and dedicated following. The main reason why there were any tapes to circulate at all for decades was due to the cult following.
- Hilarious in Hindsight:
- In this movie Ian McKellen plays a Jewish man during World War II going off the deep end using supernatural means to eliminate the Nazis. Fifteen years later he plays a former Nazi in hiding. A further two years later, he plays a Holocaust Survivor whom has powers beyond mortal men and goes off the deep end once again for a good cause. Adding to the irony, many people have compared to the design of Molasar to Apocalypse...one of the movies that McKellen didn't appear in.
- At the end of the film, he gives an epic You Shall Not Pass! speech to a demonic entity.
- Just Here for Godzilla: Quite a number of people watch the film solely for Tangerine Dream's epic score. That or Michael Mann's direction and the gorgeous visuals that come with it.
- Visual Effects of Awesome: Despite author F. Paul Wilson deriding the design as a bastard son of Darth Vader and the Incredible Hulk, the costuming and makeup designs for Molasar remain very convincing for the era the film was made, and still looks impressive compared to the modern-era motion capture effects
YMMV / The Keep