The Evil Guy (also known as the Dark Magician) is a wicked being who appears in the episode "The Enchiridion!" as the last trial to obtain the Enchiridion. He introduces two final challenges for Finn, who destroys him afterwards. For the final trail, the Dark Magician transports Finn into his "Brain World," where Finn must destroy the Heart Beast. After Finn defeats the beast with a flurry of punches to the top of its torso, the evil guy orders that, as "one last last trial," Finn must slay an unaligned ant. However, because the ant is not evil, Finn refuses to slay it. Instead, Finn exits the evil guy's Brain World, sprints toward him while screaming "NEVER!" and kicks him in the crotch, which causes the evil guy to evaporate into a red cloud of smoke, presumably vanquishing him.
- Evil Guy was portrayed by Mark Hamill, who also voiced Von Nebula in Hero Factory and Luke Skywalker in Star Wars. Hamill also portrayed the James Jesse version of The Trickster both television adaptions of The Flash in addition to LEGO DC Comics Super Heroes: Justice League: Attack of the Legion of Doom! and Justice League: Unlimited.