Time of Troubles
The Time of Troubles is the "meta-event" applied to the Forgotten Realms to explain the universe shifting from 1st edition Dungeons & Dragons rules to 2nd edition. It was caused by Ao, the Overgod of the Forgotten Realms, growing sick of the indifference of the gods to their worshippers, something catalyzed when some of the evil gods stole sacred tokens from him. As a result, he banished the gods from the heavens to the mortal world, condeming them to walk amongst mortals for a time. A huge brawl broke out, at the end of which the gods were reluctantly allowed back, after it being made clear that their power would now depend on their worshippers, and the gods of Death, Murder, Magic and Tyranny had all been killed off; the first three were replaced by mortals, the latter (Bane) would be replaced by his son for a while until a plot restored him to life at his son's expense.
The plot of Baldur's Gate, the popular D&D videogame, directly stems from this event.