Complex sentence: Two personalities, "Dennis" and "Patricia", are kept out because of Dennis's voyeuristic tendencies and obsessive--compulsive disorder, and both personalities' worshiping of "The Beast", a rumored 24th personality.
Split into simpler sentences: Two personalities, "Dennis" and "Patricia", are kept out. In Dennis's case, this is because he has both voyeuristic tendencies and obsessive--compulsive disorder, and both personalities worship "The Beast", a rumored 24th personality.