Complex sentence: Xavin journeys to Earth to find Karolina Dean, whose parents betrothed her to him, assuming that Xavin and his parents would perish while fighting the Majesdanians, their alien race.
Split into simpler sentences: Xavin journeys to Earth to find Karolina Dean. Karolina's parents betrothed her to him, assuming that Xavin and his parents would perish while fighting the Majesdanians, their alien race.