Binary Oppositions In the Descent.

Real vs Surreal: We see how there is this boundary between life in the caves for the crawlers which we see as an unknown situation, and then the real and normal life of the humans.

Hero vs Villain: Again the Crawlers against the humans.

Good vs Evil: We could again include the crawlers here, but as well, we could use this to show how Juno sends them to the wrong cave, wanting to first discover it, and then the rest of the group for trying their best to get out alive.