About 798 A.F [Reign of King Randale]
Immediately following the death of Queen Elspeth the Peacemaker the Karsites once again went to war with Valdemar, temporarily putting aside their loathing of 'witches' long enough to employ a trio of powerful mages whom they used quite effectively to press their advantage.
Herald-Mage Vanyel ultimately killed all three of the Karsite mages, but not before they exacted a terrible price in the death of hundreds of normal people and half a dozen Heralds, including Vanyel's friends Mardic and Donni.
One of those mages summoned a demon that Vanyel turned back into Karse. The death and destruction that resulted eventually gave rise to The Prophet, who preached against all magic. Eventually, he became the Prophet-King, leading a genocide against all Gifted. The war wound down as all of Karse's destructive energy was turned inward. As Randale neared the end of his life, a priesthood-controlled Karse was looking for an excuse to restart hostilities.