Erunis (Shard Ne'Vaal Supplement)
From D&D Wiki
The kingdom of Erunis was formed early in the Lost Era, from a minority group whose population and land from southeast Tyrakia had remained relatively intact through the horrible cataclysm in the Age of Flies. Unfortunately, they were invaded by arachnid forces from mad cultist indigenous tribes who had turned to dark magic for survival. As a result, the god Shabast had the entire land on which the kingdom stood sunk into the ocean, where its ruins lie to this day.