The Gauntlet of the Hero Billy was the mythical weapon of renowned hero Billy and was thought to be the only weapon that could harm the Lich. When used, it could fire extremely powerful blasts of energy.
Princess Bubblegum reveals it in one of her castle's secret rooms and gives it to Finn in the episode "Mortal Folly." Billy's gauntlet is kept in a chest, which is decorated with two green diamond-shaped studs. The chest is locked with a gold key in possession of Princess Bubblegum. It is not clear how she came into possession of the gauntlet, but according to Adam Muto, Billy may have entrusted it to Princess Bubblegum when he retired. When the chest is opened, the scene is filled with bright light, and an unrecognized voice shouts "Billy!" The gauntlet seems to possess some degree of sentience, as it sheds a tear when Finn hits it in the eye to make it stop firing a blast. In addition, the gauntlet wouldn't work for him again until he apologized. The Lich easily shatters the gauntlet to tiny pieces when Finn tries to attack him with it.
In a less noteworthy appearance in "His Hero," a young Billy is seen wearing it throughout the entirety of the "Billy's Song" montage. In the montage, Billy doesn't use the gauntlet in any remarkable fashion. Billy, being dead, currently does not own the gauntlet.
The gauntlet is silvery-blue with five fingers and a thumb. There are metal bands on every knuckle and the wrist. A blue gemstone is attached to its forearm. On the top of the hand is an eye which can open and close on its own. Like Billy, the gauntlet has five fingers and a thumb as opposed to the typical three fingers and a thumb nearly every other human and humanoid in Ooo possesses. When it is placed on Finn's arm, the gauntlet will shrink to a useable size.
- While Finn and Jake are chasing the Lich over the lake in "Mortal Folly," the gauntlet is briefly seen with seven fingers.
- Billy wears the gauntlet on his left hand, while Finn wears the gauntlet on his right hand.
- In "His Hero," the only time in which Billy is actually seen casting down the Lich, he doesn't use the gauntlet, he simply kicks the Lich.
- The gauntlet bears an uncanny resemblance to Horror's Hand, a mighty and ancient artifact from The Grim Adventures of Billy and Mandy, which also had a character named Billy.
- The gauntlet is a usable item in Adventure Time: Hey Ice King! Why'd you steal our garbage?!!
- The gauntlet bears a striking resemblance to The Symbol of Helm, a god in the Dungeons & Dragons Universe.
- The gauntlet is used as the cursor in Adventure Time Battle Party.
- The gauntlet is one of Finn's weapons in LEGO Dimensions.