Lord Montymort

Lord Montymort was an evil dark wizard who decided to capture Lisa in order to use her magic powers to increase his own.

Treehouse of Horror XII
Bart assists Montymort in capturing Lisa. At Springwart's Magic Recital, Lisa is about to perform the "levitating dragon trick." Bart, meanwhile, is backstage, stealing Lisa's wand and leaving a licorice Twizzler in its place, before sneaking away.

The curtain goes up, and Lisa orders stagehands Jimbo and Kearney to release the dragon. As the dragon roars and breathes fire, Lisa picks up her wand and calmly says the levitation charm, but nothing happens. Then she notices the licorice stick, and sees Bart backstage laughing evilly. The dragon now reveals its true colors and morphs into a giant Montymort, who grabs Lisa and puts the connected helmets onto her head and his own. As the lumps start flowing from Lisa to Montymort, Lisa calls to Bart for help. Now remorseful, Bart casts a spell with Lisa's wand: "Prank be undone! Destroy the evil one!" However (possibly due to his not being specific enough), the spell zaps Bart instead of Montymort, scorching Bart and charring the wand.

Giving up on magic for the moment, Bart charges at Montymort and stabs him in the shin with the charred wand. As it turns out, he's found Montymort's one weakness: his enchanted shin, the source of his power. Montymort shrinks to normal size and dies, and Slithers eats him whole in typical snake fashion, sobbing all the while.