Complex sentence: But once in a while, he will scare people on Omegle, a site where you are paired with another random person with a web cam, he will dress up as one of his characters and try, mostly succeed, to scare them.
Split into simpler sentences: But once in a while, he will scare people on Omegle, a site where you are paired with another random person with a web cam. He will dress up as one of his characters and try, mostly succeeding, to scare them.