The Deadlands Chronicle
The event known as the Profound Disjunction lead to the fall of the Magic Empire of Kalesh-Tar. The specifics of what transpired are unknown, and since no records from the end of the Age of Magic are known to have survived the Magic Empire’s fall, the mystery is unlikely to be solved.
The Profound Disjunction is so named because it was the event that disjoined the threads of the Web of Life, which effected the entirety of existence on the most fundamental level. Simply put, the Profound Disjunction was the death of magic in the world.