One of the "villains" is twisted in part because of the abuse he and his mother suffered at the hands of his father. The witch is forced to kill her own child, and several other children are killed before things end.
The witch, Katherine, is tormented by the teens for fun. In one instance, one of the boys cuts off her clothing and then slices through her breast with a blade just to prove that he can.
From the beginning of the book, the witch's eyes are sewn shut. There is a good amount of eye mutilation for our main characters in the latter half of this book with graphic descriptions of the damage.