Karsus's Folly was a cataclysmic event that struck the world of Toril in 507 BA (-339 DR).
The Archmage Karsus, trying to save the Empire of Netheril from a war with the malevolent, slug-like Phaerimm, cast an extremely powerful spell meant to turn himself into a god. His plan was to seize control of magic itself from the goddess Mystryl and use it to ensure victory for his people. However, the process instead killed Mystryl and left Karsus overwhelmed by the raw, vast power of the world's magic. Unable to control it, magic briefly ceased to work, causing devastation across the spell-dependent lands of Netheril, destroying the empire, and killing Karsus. Mystral quickly reincarnated as Mystra and restored magic to Toril.
Effect on Eamon
The event temporarily collapsed the Green Gate, a longstanding natural rift connecting the city of Lumen on Eamon with the eastern High Woods on Toril. Reforming after several minutes, it now opened onto a world disrupted by Karsus's Folly.
