The Arumsfall

The Arumsfall was perhaps the greatest defining moment of recorded history, when the entire nation of Arumnia was violently plunged beneath the waves of the ocean, bringing about the deaths of untold millions, and ushering in the Second Scourge.
  The Empire of Arumnia would not survive this destruction, already fracturing at the edges of its territory after the Great Scourge, the loss of its homeland saw the absolute collapse of Imperial authority and political hegemony across the entire length of the Empire.
  The Church would survive this collapse, emerging stronger, but from this point forward no single political authority would reunite the former realms of the First Empire up to the present day.