Most likely Voldemort’s closest companion, Nagini was a Maledictus who had once been a human woman but due to this blood curse was now permanently a snake – losing all sense of humanity. As a snake, she was always at Voldemort’s side and one of the only people or creatures that he showed any affection towards. One reason why he kept her close was due to the fact she housed a piece of Voldemort’s soul – making her a Horcrux.