He was played by Roland Smith.
As explained by Wilhemina Setterwind at the conclusion of the episode, Badge is the corporeal manifestation of the evil part of the Setterwind family magic.
He had apparently captured and killed many by hanging them, given that his lair (Which he refers to as "My garden") is filled with dangling skeletons strung up from nooses. His one goal is to completely take over the Setterwind family magic, which can only be achieved by defeating the mistress of the magic and claiming the power of her Jasper's Light amulet as his own. However, Celina Setterwind, the very first witch in the Setterwind family line, was able to imprison him in a containment crystal, and even came up with a magic spell to help her descendants against him if he were to escape.
During the events of the episode, Trevor Setterwind accidentally freed Badge through fooling around with the Setterwind Flute. One blow on it was all it took to release him, and he sought revenge against the Setterwind family by plotting to steal the family magic for himself. After tricking Trevor's older sister, Gwen (who was, unbeknownst to him at that time, the new heiress of the Setterwind magic), into letting him into the house, he took Trevor hostage and demanded to be given the Setterwind magic in exchange for him.
Though she was initially terrified and confused by her current situation, Gwen came to realize - through a book that was amongst the family heirlooms that Willie had given her - that she was the new Setterwind witch whom Badge was referred to, and that there was a spell she could use to contain him. After memorizing the spell and tying her Jasper's Light amulet around her neck, she went back to his lair to confront him. However, it turned out that her magic was not yet strong enough to fully utilize her amulet against him. Fortunately, Willie showed up in the nick of time and told her to use her gift of music with the Setterwind Flute.
Badge prepared to steal the magic from Willie's amulet, only to realize that it was too late, for she had already passed the magic down to Gwen. As Badge cowered in terror, Gwen started to play on the Setterwind Flute, and as she played each note of his name (B-A-D-G-E), he was forcefully transported back into the containment crystal. With him back in his imprisonment where he belongs, Willie then explained to Gwen more of her family legacy, and the responsibility Gwen now has to use her newfound power to help ensure that Badge never escapes again.