Floods!

Geological / environmental event

There were three moons, ... previously.

Because of some reason, which one is unknown to the peoples of Xiantar, one of the three moons vanished. Shortly afterwards, tremondous waves crushed against all continents and islands, swallowing up some of the smaller islands of Astar and Fron. Water rushed over the lands, crushing buidlings, crumbling mountains. In its retreat, it formed ravines, hills and deep river basins. But it not only shaped the continents to the form they have today, it also eliminated many civilizations living close to the ocean. Amongst others, the largest civilization ceased its existance. Little can be found of them today as they were a strong nation living off of the sea and being proficient of advanced seamanship. This nation, called Eletra, was the ruling people of Xiantar. But surprised by the giantic force of nature, most of its people died.