Complex sentence: The history of the Jaredites was reportedly recorded by a Jaredite prophet named Ether, whose record was abridged by the prophet Moroni (son of Mormon) many hundred years later and included in the Book of Mormon as the Book of Ether.
Split into simpler sentences: The history of the Jaredites was recorded by a Jaredite prophet named Ether. His record was abridged by prophet Moroni (son of Mormon) many hundred years later and included in the Book of Mormon as the Book of Ether.