Kor Alanth was a small, but immensely powerful island city-state situated in the center of the inner sea. Their trade-fleet ruled the economy of every nation within reach, and their massive mystical might kept any grumbling from other countries strictly to a minimum. Kor Alanth, in a very real way, ruled the world. All it took was a single artifact to bring it all crashing down.
No one still living knows which member of the Council of Archmagi created the Device. It was a portal, powered by the ambient magic of the land itself, and it could open a path to any of a thousand planes, a million worlds. It was supposed to usher in a new era of trade and exploration for the empire of Kor Alanth. Instead, all it brought was destruction. As the artifact powered up, it shredded the barrier between worlds. Hordes of the undead and the damned swarmed across the lands. Elemental storms incinerated nations, and buried cities beneath waves of water and stone.
The Archmagi, horrified at what they had wrought, tried to turn the portal back off. They were unsuccessful. It was gathering more and more power, attempting to stabilize itself, and failing. Soon it would detonate, wiping Kor Alanth, and the island upon which it was built, from the face of the world. Quickly, the council put a number of doomsday plans into action, each meant to preserve some portion of their society, history, and people. You are part of one of those plans, thrust into the future with other refugees, in the hope that you might make a new home, and remember the ideals, and the hubris, from which you came.