Complex sentence: In the Age of Apocalypse Ship was nearly destroyed by Magneto when it endangered the lives of his X-Men after they successfully thwarted the plans of En Sabah Nur's Horsemen to take control of the United States Nuclear Arsenal.
Split into simpler sentences: In the Age of Apocalypse Ship was nearly destroyed by Magneto when it endangered the lives of his X-Men. This was after they successfully thwarted the plans of En Sabah Nur's Horsemen to take control of the United States nuclear arsenal.