Complex sentence: Rob breaks a hole in the wall and asks Everett what is behind there, who admits that there is The Beast's torture chamber and they fed a lot of misfortunate girl to him, although they did not know that The Beast indeed grabbed those girls.
Split into simpler sentences: Rob breaks a hole in the wall and asks Everett what is behind there. Everett admits it is The Beast's torture chamber and they fed a lot of misfortunate girls to him, although they did not know that The Beast indeed grabbed those girls.