Who ended up being the Devil in Devil?

Who ended up being the Devil in Devil? I have really no interest in going to see this movie but I want to know who the Devil was in the movie. ALBEIT, seeing as how it's an M. Night Shyamalan movie the Devil is probably like their deepest sins or whatever, OR all of them combined, cuz his movies ALWAYS have some kind of moral played out within the movie that ruins the movie in every way possible.... BUT can somebody PLEASE tell me the ending result? I tried searching it up on Google and nothing that helped me in the least bit came up in my search. :/ Grazie!! :)