Magical Histories, Volume 3: The Second Sundering
In the years following Mystra's assassination, the planes of existence were in upheaval. Lord Ao, the Hidden One, overgod of all deities and mortals, sought to rebalance what had been thrown into disarray, by renewing the Tablets of Fate - those most sacred of artefacts between order and chaos. The very portfolios of the gods were rewritten, and several who were thought lost found themselves returned to life and power. Heralded by the wizard, Elminster Aumar, Mystra found her magic restored, and portfolio returned to her. Once again, the rightful goddess of magic found herself to be custodian of the Weave.