"It was just us!"
There is no it! Do you think it's possible the supernatural element of the show will turn out to be a coping strategy for the trauma, the deeds they were forced into, and/or mental illness? I've thought about this as the show goes on. Or maybe the supernatural element is a metaphor for trauma?
I also think whatever is in the wilderness could have chosen these girls specifically because they have something inside of them that it's drawn to.
The scene where Tai is watching her grandmother die early on makes me think it could be the latter.