Mermaid

A mermaid child who was held captive in a ghost ship, her flute music appears as SOS signals to other ships and thus draw them near for the evil within the ship to feed on their souls. As she exchanged her will to talk for a human body to be with her love, she would die the moment she utters a word. However, as events unfold with Keziah sent to retrieve her on his master's order, she was forced to speak to save his life and was revived as Emile's blood warrior.

[Spoiler] Her name is finally revealed as a dying Emile relinquished Madeleine to Sylvia. [/Spoiler]

(Source: Wikipedia)