The High Priestess is the birth mother of the daughters of Aku as well as the leader of the all-female cult of Aku.
Her appearance was unknown but a silhouette of her was shown when she was giving birth to her seven daughters naked. Like other members of the all female cult of Aku, she wears a black robe and a pink mask reminiscing of her master.
She proves to be merciless even to her biological daughters as she punishes them violently if they make any mistakes. Her only loyalty lies with Aku.