The Grand High Witch, appearing in The Witches, is the head of all of the witches in the world and the main antagonist in the film. When interacting with normal people, she appears as the attractive if aloof Miss Eva Ernst, head of the Society for the Prevention of Cruelty to Children. Beneath her skin mask and aristocratic air, however, she is a bald, warty, dictatorial crone, with an elongated nose, loose hanging skin, and the traditional long fingernails and stumpy feet of all witches.

She, along with the other witches, hates children and seek to destroy them. She planned to turn every child in England into mice, and turned the main character, Luce, into a mouse, along with another boy named Bruno. She shows her sadistic side when she pushs a baby in a stroller down a hill so that Luce will come out of his hiding place.

She has a personal assisstant named Anne Irvine, who s implied to be a good witch because at the end of the film she turns Luce back into a boy.

The Grand High Witch is killed when she is turned into a mouse with the other witches.