Sunken Journal from Duke, a Mystery of the Shrine of Flooded Embrace.
They were known as Sirens and they had a king and queen. The king was murdered by the Ancients and the queen's rage was a thing to behold. She cursed the Ancients and they became ill. I haven't been able to discover exactly what happened, but it sounds unpleasant. But even this didn't satisfy the Sea Queen. She wanted to find a way to punish those who had wronged her, for all eternity. Her desire for revenge led her to explore the forbidden powers of her people, searching for perfect punishment.