Freya Jennings

 was a member of HMS Aquitaine. Tegan Jovanka observed a time echo of her. According to Hargreaves she disappeared when a gravitational wave hit from the nearby black hole. She had been infected by deliberately by Sergei Akunin with his first hybrid of the Akunite. She fully mutated but retained her memories and attacked Akunin. The Doctor rescued her from the black hole before she could be infected the Akunite. (AUDIO: Aquitaine)