Mother of Mine
Mother/Wife of Mine was the matriarch of a criminal family known only as the Family of Blood. She resembled a gaseous entity prior to possessing Jenny, a maid from the Farringham School for Boys.
Her family attempted to take the Tenth Doctor's life essence. After they were defeated by the Doctor, Mother of Mine was thrown into the event horizon of a collapsing galaxy, to be shown how horrible it is to live forever. Her husband, son and daughter underwent similar punishments. (TV: Human Nature/The Family of Blood)
Personality
Like the rest of her family, Mother/Wife of Mine was a pitiless and merciless killer and never hesitated to kill anyone who stood in their way.
She possessed an intense sadistic streak and occasionally displayed signs of insanity. She gleefully told Martha about Jenny’s last moments before she took her body and “consumed” her and how terrified Jenny was with a large smile on her face. She also laughed insanely at the sight of the Headmaster running back into Farringham School after Son of Mine had just murdered his colleague.
The only beings she displayed any sort of affection for were her family and she was finally horrified when the Doctor punished her with eternal imprisonment and separated from the rest of her family.
Behind the scenes
Mother of Mine is one of the enemies in Doctor Who Legacy mobile game.