Ruth is a loyal and protective familiar in the anime series 'Mahoutsukai no Yome' (The Ancient Magus' Bride). Originally a black dog, he becomes Chise Hatori's familiar after a series of events that reveal his deep connection to her. Ruth is able to transform between his human and canine form, serving as both a companion and a guardian to Chise. His calm and collected demeanor balances Chise's impulsiveness, providing her with emotional support throughout her journey in the magical world.