The Time of Troubles

The Time of Troubles refers to the year 1358 DR, when the Tables of Fate were stolen and Ao punished the gods by exiling them from their realms and leaving them to roam the Prime Material Plane.

Cause
The gods Bane and Myrkul stole the Tablets of Fate from Ao in an attempt to diminish his power. The Tablets of Fate were tablets upon which official records of the deities' portfolios and ascensions to godhood were kept. Upon discovering they were, Ao called forth a meeting of the gods. No one would confess to the crime, and so they were all cast down from the heavens, sent to walk Faerûn and learn humility.

Effects on the Material Plane
During the Time of Troubles, magic was wild, hardly operated at all for clerics, and deities walked the material plane.

The adventuring party consisting of Cyric, Kelemvor, Midfire, and Adon set out to recover the missing Tablets of Fate and supposedly succeeded. However, the Tablets' ultimate fate is unclear.

Consequences
Ultimately, Cyric slayed the god Bane. He ascended to godhood and was granted his entire portfolio. Ao deemed Midfire fit for the position of Mystra, goddess of magic, and gave it to her.

The gods returned to their realms upon Cyric and Mystra's ascension to godhood.