Complex sentence: Noctis Lucis Caelum is the only son and heir of King Regis Lucis Caelum CXIII of Lucis, the last kingdom in the world to possess a crystal, as those belonging to other countries have been lost through a protracted cold war.
Split into simpler sentences: Noctis Lucis Caelum is the son and heir of King Regis, ruler of the country of Lucis. His country is the last in the world to possess a crystal, as those belonging to other countries have been lost through a protracted cold war.