A hag is a wizened old woman, or a kind of fairy or goddess having the appearance of such a woman, often found in folklore and children's tales such as Hansel and Gretel. Hags are often seen as malevolent, but may also be one of the chosen forms of shapeshifting deities, such as the Morrígan or Badb, who are seen as neither wholly beneficent nor malevolent. (source)