I picked up my copy of Grand History of the Realms over the weekend, and with all the debate that's occuring... May as well add fuel to the fire. 
Spoilers... (highlight to read)
Spoilers... (highlight to read)
In 1384 DR, Tyr kills Helm in a romantic misunderstanding over the heart of Tymora. Though nothing can be proved, the gods believe that Cyric is somehow involved in Helm's death.
In 1385 DR, With help from Shar, Cyric murders Mystra in Dweomerheart, destroying the plane and Savras, as well as sending Azuth and Velsharoon into the Astral plane.
Magic bursts from the bonds of the Weave. Thousands of mages are driven insane or destroyed, and the very subsatnce of the world becomes mutable beneath the veils of azure fire that dance across the sky.
Cyric is imprisoned on his home plane for 1000 years by Tyr, Lathander, and Sune for his crimes. This event is what is known as the Spellplague
In 1385 DR, With help from Shar, Cyric murders Mystra in Dweomerheart, destroying the plane and Savras, as well as sending Azuth and Velsharoon into the Astral plane.
Magic bursts from the bonds of the Weave. Thousands of mages are driven insane or destroyed, and the very subsatnce of the world becomes mutable beneath the veils of azure fire that dance across the sky.
Cyric is imprisoned on his home plane for 1000 years by Tyr, Lathander, and Sune for his crimes. This event is what is known as the Spellplague
