A war between Eldemar and various necromantic nations, won by Eldemar.
In the background there were many succession crises from people who realized they would never rule because their parents or siblings were undead. The common people hated being ruled by undead. Eldemar was getting involved in wars to prove their supremacy.
Sulamnon rose in rebellion against their crown, supported by Reya and Namassar, and lost. Eldemar then tried to force them to ban necromancy.
The necromancers in Sulamnon refused to accept the treaty and raised an army of their own, bolstered by the part of Sulamnonian military that still felt they had a chance to win if they continued fighting. Soon, they were joined by other forces that resented Eldemar's growing power - the remaining Khusky tribes that still retained some military might, the remains of witch covens, the undead aristocracy of other countries that saw the way wind was blowing and wanted to overrule the precedent that would see them similarly disposed of, as well as a number of opportunistic actors that felt they had more to gain by siding with the necromancers than with the king of Eldemar. The Necromancer's War had begun.
The necromancer's brutality and cruelty quickly swayed neutral parties against them, weakening their coalition.
Eldemar's general Fert Oroklo defeated the necromancer's army led by Quatach-Ichl, thereby destroying them as a coherent force, the continent sighed in relief. The kingdom of Eldemar rewrote the map in their favor, and were seen as heroes for it instead of tyrannical aggressors, and the surviving parts of the necromancer's army fled to the frozen island in the north that would be henceforth known as the isle of the exiles - Ulquaan Ibasa.