Klarion the Witch Boy is a supervillain that appeared in The New Batman Adventures episode "The Demon Within". He is voiced by Stephen Wolfe Smith.
Klarion the Witch Boy is considered one of the most dangerous beings in the magical community. Klarion arrived on Earth from another dimension called Witch World of the Beyond Country. Klarion, having reduced his parents to mice, fled from the Witch World's Elder Judges after he stole the Book of Forbidden Secrets. Jason Blood unwittingly helped Klarion escape his pursuers. Klarion mockingly calls him 'uncle' and their constant battles followed. Klarion is accompanied by his familiar, Teekl the cat whom also has a talent for magic.
Klarion encountered Blood once again at a Gotham City auction. They bid against each other for the personal branding iron of Morgaine le Fey only to be outbid by Bruce Wayne. Klarion later sent Teekl to steal the iron. Klarion then used the item to separate Etrigan from Blood and enslaved it. Klarion went on a brief rampage through Gotham until Batman arrived and tried to retake the iron. After Blood and Etrigan were reunited, Klarion was 'grounded.'