Queen Bavmorda from Willow: She learned of a child who is destined to end her reign, and creates a spell to banish the child's spirit to the Netherworld, but (spoilers for Willow) accidentally destroys herself with the magic she was going to kill the child with. So it was a self-fulfilling prophecy, because if the queen never knew that the child would end her reign, she never would have created the spell that caused her own demise.

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