Metaphysical / Paranormal event
After almost two hundred of years of naval clashes, the Leviathans of the Deep reawaken. During a major engagement near the middle of the Ymmari Bay both navies are destroyed as beasts of the sea converge on the naval battlefield. Few escape to tell the tale. Few naval battles and incursions are attempted after this, and always with the same result; utter destruction.
In addition, great storms start to arise without warning, and the Ymmari Bay is renamed, "The Bay of Tempests".