wtf was that thing at the end?

First off I'd like to say this was one of the most unsettling films i've ever watched, I didnt like it at all, the death scenes were pretty horrific, I mean I can deal with body gore but the "realistic" deaths like this are really sickening, it was just generally really horrible movie in the sense that the subject matter and how it was all played out really disturbed me. Also the damn ringing every time her dad was around drove me crazy!

Anyway, what the hell was that thing with the huge head that molly walked too at the end?

I taught you everything you know, but not everything I know.