Who is Warren Jeffs from Under the Banner of Heaven: A Story of Violent Faith and what is their importance?

Warren Jeffs is the prophet who takes over control of Colorado City and Bountiful when his father "Uncle Rulon" dies in 2002. The people don't have the affectionate relationship with him as they did with either Rulon or Roy. Jeffs controls his people through fear and dread. Many of the Mormons under his control do not respect him and long for the day when his rule will be over.