The Descent is set in the same shared universe as all of the following...
- Keepers Of The Lost Cities (Book Series)
- Apocalypto
- Solomon Kane (2009)
- Centurion
- Bone Tomahawk
- The Revenant
- The Shield
- Breaking Bad, Better Call Saul and El Camino: A Breaking Bad Movie
- Sons Of Anarchy and Mayans MC
- Transformers Prime
- Dog Soldiers
- Deathwatch
- Overlord
- The Mummy (1999)
- King Kong (2005)
- Tales From The Crypt Presents Demon Knight
- Pair Of Kings
... how is this unironically the only good WMG on here with this movie.
The film takes place in Minecraft
- And the crawlers are creepers.
Alternatively, the film takes place in Skyrim
- The crawlers are the falmer: a lost humanoid race who have gone blind and locate themselves by sound.
Sarah is in a coma after the car crash, and all the characters, including people she knows, are representations of parts of her psyche, and the events of descending into the cave is her mind's representation of slowly descending into death, the death of the characters representing the death of those parts of her brain (NOTE: Applicable only to this film, ignoring the sequel).
Sarah actually did escape the cave.
But Juno's vengeful ghost takes her by surprise in the car, seizes supernatural control of her sensory input, and makes Sarah think she's still down there. The crawlers are the descendants of the Lost Roanoke Colony.
The colonists were forced to live in caves, they went insane and mutated , becoming the first crawlers. Over time, more people got lost in the caves and joined their ranks.