Estela Arbizu

Estela Arbizu is the darklord of Marina and a Ravenloft Siren. She was once a beautiful human woman, but grieving the loss of her father and husband, both sailors, to the sea, she began murdering sailors to deny the sea goddess Ny her claims over them. When Estela fell in love with yet another sailor, she decided to try to kill Ny herself. Estela called Ny forth with a summoning ritual and attempted to slay her using a harpoon covered in the blood of her own mother. The harpoon did not fell Ny, and the sea goddess, angered by Estela's transgressions, cursed her to become a Ravenloft Siren. Note that Estela Arbizu was never updated to 3e, so any creature types are speculative.