The Lich

"The Lich" is the twenty-sixth episode and season finale of the fourth season of the American animated television series Adventure Time. The episode was written and storyboarded by Tom Herpich and Skyler Page, from a story by Patrick McHale, Kent Osborne, Pendleton Ward. It originally aired on Cartoon Network on October 22, 2012. The episode guest stars Lou Ferrigno as Billy, and Ron Perlman as the Lich. The series follows the adventures of Finn, a human boy, and his best friend and adoptive brother Jake, a dog with magical powers to change shape and grow and shrink at will. In this episode, Finn has an ominous dream about the Lich, and sets off with Jake to warn Billy. Billy reveals that they must unite the gems of all the crowns of power, place them in the Enchiridion, and open a portal to the multiverse. However, it is revealed that the Lich is actually disguised as Billy. Finn and Jake then follow him through the multiverse. "The Lich" would be the inception of a three-episode arc that would not be concluded until the second episode the fifth season.