The ancient Netherese had established the splendour of the arcanists. In the period of darkness after the dusk of the gods, the arcanists had saved the commoners from savagery and foolishness, building a civilisation the gods themselves feared!
Combined with their flying cities, ancient great arcanists had the power to kill gods themselves! The gods would not stand such an affront to their existence, and the arcanists who coveted origin force and touched on several taboos were exterminated.
However, that very war that had destroyed the Netheril Empire had also gravely hurt the gods. Many had fallen, and the numbers of gods decreased without end.
Because of this painful lesson, the arcanists became taboo and were annihilated by numerous churches. All tomes related to the Netheril Empire were destroyed, creating another era of savagery.
One flying city of the arcanists had managed to survive that period, and at a specified time it had returned to the prime material plane....