The history behind that is on the Tibia's lore , I leave you the text above:
Yet, I do sense it as well. Evil is slowly eating its way into the life and soul of Kilmaresh. So my time is short for my help is needed direly here. At this very moment, I'm trying to gather evidence to unmask a traitor who's consorting with the forbidden cult of Fafnar. Those cultists have turned into a real threat. They are corrupting the hearts of more and more living creatures here.
Alas, there came a time when a group of Fafnar's adherers became more and more influential and aggressive until they postulated the sole worship of Fafnar. This resulted in a civil war between the Fafnar followers and those who fought for the duality of the two sun gods. Ultimately, the war was ended by Suon himself. He split off the eastern peninsula from the western part of the landmass by a strait, destroying the former capital Nuur. This event has been known as Suon's Wrath ever since.