Complex sentence: The highest class of Warrior-Servants was known as the Prometheans, page 59 and were once been in high social standing and power, serving in various roles in the Forerunner Council.
Split into simpler sentences: The highest class of Warrior-Servants was known as the Prometheans, page 59. Prometheans once held high social standing and power, serving in various roles in the Forerunner Council.