Signy Volsung was the daughter of Volsung in the "Saga of the Volsungs". She was married to King Siggeir who was the murderer of her father. Signy murdered two of her children with Siggeir, had a child through her twin brother, and burned Siggeir alive in his hall before walking into the flames and killing herself. Signy is pronounced "SEEG-noo" in Old Norse. I love this name. It's malevolent and powerful. Perfect for a fantasy character.