Thera

Thera was a territory of mountains and forests, that was home to early Featherfolk and high elf cultures, including the mighty Union of Eldar.
In the upheaval of the Cataclysm. Thera - along with Remar and Dakhaz - was devastated. Much of the east collapsed into the sea and the mountain home of the Featherfolk slid down to create new shorelines and reefs. As the continent was crushed, new mountains buckled up. As mighty as they were, the cities of Thera were utterly destroyed. Millions died.