Mommy Fortuna
Mommy Fortuna is the tertiary antagonist in the novel and animated movie The Last Unicorn. She is a witch who uses her illusory magic to run the Midnight Carnival, which showcases mythical creatures that are, in truth, just normal animals disguised by her spells. However, her magic only works on weak-minded people who believe whatever comes easiest.  She herself appears as the climax of her own show, disguised as Elli, the spirit of old age.

She manages to capture two real mythical creatures for her show; the first is the Harpy Celaeno, the second is the Unicorn of the title.  She knows her magic is not strong enough to keep them captive, but she sees these two as her only claim to fame and chooses to keep them even if it means her death.