The fall of the magical college of Occiarim. Their scholars succumbing to the darkness of lore magic
Occiarim continually pushed the bounds of magical discovery. Until one fateful experiment opened a portal to lore, tearing the fabric of reality in several places, the spores of lore infected the scholars there and caused them to push plagues and undead abominations on the peaceful people of the world. And so Occiarim fell, its walls and ceilings collapsed to protect those on the outside. Dooming those within.