The Sea of Fallen Stars was the largest inland body of water in Faerûn. The sea served as a crucial trade way for the powers of central and northern Faerûn and beyond.
In the autumn of 1485 DR, the Great Rain began to fall around the Sea of Fallen Stars and continued unceasingly for over a year. This constant storm caused massive floods; thousands perished from drowning, lightning strikes, or bursts of wind that capsized ships. By the time the rain abated, the Sea of Fallen Stars had swollen back to something approximating its former size, flooding vast tracts of land and numerous cities beneath the waves.