Complex sentence: They realized that are trying to catch a supernatural being, Satans emissary-Prosatanos, who tried to keep control the world in the time of crusades, but he was stopped by King Richard for centuries.
Split into simpler sentences: They realized that are trying to catch a supernatural being, Satans emissary-Prosatanos. He tried to keep controll over the world in the time of crusades, but he was stopped by King Richard for centuries.