Complex sentence: During this time the Grey Draconium Dragons Constructed the Horn of Libris and gave it to the Dragon Booster telling him to use it when the time was right, the Dragon Booster entrusted the Horn to the Energy Booster.
Split into simpler sentences: During this time, the Grey Draconium Dragons constructed the Horn of Libris and gave it to the Dragon Booster, telling him to use it when the time was right. The Dragon Booster entrusted the Horn to the Energy Booster.