A Banshee was an Irish spirit. Its cry heralded death.
A Banshee came to herald Martha's death when Victoria Waterfield was staying at Cormac's home. Victoria screamed when she saw the Banshee. She saw the face every time a family member died, and screamed whenever she saw the Banshee. After three deaths, the Banshee came to take Victoria as one of its own, as her screams had heralded several deaths. When the Second Doctor saved the life of Niall, the next victim, the Banshee shrieked and disappeared. (PROSE: Screamager)