In The Mythic Tarot by Sharman-Burke and Liz Geene, the Moon Card depicts the goddess Hecate as a mysterious female figure with three faces, crowned by the diadem of the moon in its three phases. In Greek mythology, Hecate was ruler of the moon, magic and enchantment who became one of the Underworld Rulers, sometimes called the Invincible Queen.
The three faces represent the three faces of the feminine, the virgin, the mother and the old crone, and symbolise the stages in life: youth, middle age and old age. As the moon is ever changing through its phases, so life also changes.