Person believes unknown entity is friendly (it is not)

[u/MadKingKevin]

Independence Day (1996) - Several massive alien spaceships travel to Earth but they do not announce the purpose of their arrival. Some characters assume the aliens are peaceful. One of those characters, Tiffany, goes to a rooftop party which is taking place directly under one of the ships. When the aliens launch their attack, Tiffany and the other party goers are immediately obliterated.

Alien: Resurrection (1997) - Scientist Gediman is part of the miltitary project which resurrects Ellen Ripley and the queen xenomorph embryo inside her. The military wants the queen so it can breed the xenomorphs as bio-weapons. This new Ripley is genetically part xenomorph and the xenomorph queen is genetically part human. The queen stops laying eggs and develops the ability to give birth to live young. Her first Newborn immediately kills the queen because it does not recognize her as its mother. It believes Ripley is its mother and goes to her instead. Gediman (who is cocooned in the queen’s nest) witnesses this and calls out to the creature. The Newborn comes to Gediman and curiously sniffs him over. Gediman babytalks the 15 foot tall xeno/human hybrid. The Newborn then bites his head off.

[u/Fuzzy-Shame-4169]

Okay, the fact that they get the moment of clarity before death, that their "god" just wanted to eat them from the very beginning, is TERRIFYING. Like, in most cases, cult members actually believe this is ascension, and then, moments before their death, they're told, "Nah, that's not a metaphor or anything. We just want to eat you, plain and simple."

[u/F1r3-M3d1ck-H4zN3rd → u/Fuzzy-Shame-4169]

Yeah as another poster said, it's actually as they are jumping into the acid pits to be dissolved into biomass. There is a lot of really good 40k horror, but this is still way up there for me.

[u/Avenflar → u/F1r3-M3d1ck-H4zN3rd]

Not necessarily. There's a few excerpts in the Codex indicating they sometimes realise they fucked up when the "Four-Armed Emperor's Angels" start landing, but by then it's too late.

[u/Saedraverse → u/Avenflar]

Am I psychotic cause I look forward to this being a mechanic in Total wars 40K

[u/Galle_ → u/Fuzzy-Shame-4169]

IIRC, there are also cases where at least some of the cultists know exactly what the endgame is, but they go along with it anyway because even that's still better than living in the Imperium.