The Gauntlet of the Hero

The Gauntlet of the Hero 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.

Episode appearances
Princess Bubblegum reveals it in one of her castle's secret rooms and gives it to Finn in the episode "Mortal Folly"; 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. 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 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 currently does not own the gauntlet.

Appearance
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.

Trivia

 * 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, but Finn wears it on his right. It is possible there were two gauntlets, and the one worn in "Mortal Folly" was part of a pair with the one in "His Hero."
 * In "His Hero," the only time we see Billy actually cast down the Lich, he doesn't use the gauntlet, he simply just kicks the Lich.
 * The Gauntlet of the Hero 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 useable item in "Hey Ice King! Why'd You Steal Our Garbage?!!