Complex sentence: Elgo tells the party that he wished to use the crystals to achieve immortality, and that the crystals, sensing his purpose, split the world hoping to halt his plans, consequentially splitting what good remained in Elgo away to form the Mask.
Split into simpler sentences: Elgo tells the party that he wished to use the crystals to achieve immortality. The crystals sensed his purpose and split the world hoping to halt his plans, consequentially splitting what good remained in Elgo away to form the Mask.