Complex sentence: At some undisclosed time Dark Beast left the Age of Apocalypse and returned to Earth-616 Universe where he is approached by the AoA version of Nightcrawler who wanted in turn to return to their home dimension.
Split into simpler sentences: At some undisclosed time Dark Beast leaves the Age of Apocalypse and returns to Earth-616 Universe. He is soon approached by the AoA version of Nightcrawler who wants to return to their home dimension.