The Spellplague was a cataclysmic event, beginning in the year 1385 DR, triggered by the murder of [[Mystra?]], Goddess of Magic, by the Mad God Cyric.

It affected the entire world of Toril, and over the course of ten or more years it greatly transfigured the surface of the planet and the use of magic.

However, by the year 1479 DR (the beginning of the Tyranny of Dragons campaign) the world has largely recovered and in large part returned to its pre-Spellplague configuration.

Behind the DM’s Screen

The publication of D&D 4th Edition in 2008 required the Forgotten Realms to be changed in drastic ways to accommodate the new 4th Edition design philosophy, including the introduction of new races such as Tieflings and Dragonborn, and the addition of large blank areas to the Forgotten Realms map to justify the new “Points of Light” campaign philosophy. The Spellplague was in the in-universe explanation for these changes, along with an advancement of the Forgotten Realms timeline by around 100 years.

D&D 5th Edition largely returns to the philosophy of previous editions (although Dragonborn and Tieflings stuck around) and so by the time of our campaign most of the effects of the Spellplague have been undone and the Forgotten Realms are largely recognisable to players who adventured in the pre-Spellplague world.

Define external redirect: Mystra