Mother of Mine

Mother/Wife of Mine was the matriarch of a criminal family called the Family of Blood. She resembled a gaseous entity prior to possessing a maid named Jenny.

When she was caught by the Tenth Doctor, after she and her family tried to take his life essence, she was thrown into the event horizon of a collapsing galaxy, to be shown how horrible it can be to live forever. (DW: Human Nature/The Family of Blood)