“Brrrrooo ha ha ha ha... A touching scene, to be sure.”
Bonechill is an enemy in Super Paper Mario and the boss of Chapter 7. He is a massive, undead dragon with a large, blue-scaled head, six small, white-feathered wings on his back, and a large golden cannon with two wheels for a lower body. He is the leader of the Skellobit army and attempts a takeover of The Overthere. According to The InterNed, his theme is called "Bonechill Appears".
Tippi's tattle implies that Bonechill was once a Nimbi, which is supported by the fact that he speaks in antiquated English like them and has feathered wings on his back. This fits into the overall motif of The Underwhere and The Overthere, which draw heavily from both Ancient Greek mythology and the Christian religion. In particular, the concept of a fallen angel (Nimbi) is inspired by the Biblical story of Lucifer, who became the devil after betraying God. Furthermore, in Dante's Inferno (of the epic Italian poem, the Divine Comedy), Lucifer (now known as Satan) is depicted as a giant, six-winged beast imprisoned in ice in the deepest circle of Hell. This is all paralleled by how Bonechill has six wings, was imprisoned deep below the Underwhere, and is a self-styled "master of the cold dark" who is "something of an evil celebrity in certain circles of the Underwhere". Similarly, his being released during an apocalyptic event (the emergence of The Void) may be derived from the Book of Revelation, where Satan escapes from hell and he and his army are battled and defeated in heaven.
Before the outset of Super Paper Mario, Bonechill and his army was trapped in a prison below The Underwhere. Count Bleck set him free to defeat Mario, although Bonechill also claims to be seeking the Pure Heart in order to use its power for himself. Ultimately, Bonechill failed in his attempt to destroy the Heroes of Light and seize control of The Overthere and The Underwhere, as his army was defeated and he himself was shattered to bits by Mario and his companions.
In battle, Bonechill fires large ice bullets from his cannon and attempts to freeze the heroes with his icy breath. If he freezes one of the heroes, they will start taking four damage points a second, the highest amount of freezing damage in the game. Bonechill can also use his breath on the ceiling to create icicles that will fall and damage the player if they are standing underneath. Bonechill's only vulnerable point is his head, which is out of range for most of the player's conventional attacks. However, Thoreau can be used to grab the ice bullets and icicles, allowing the player to throw them at Bonechill's head for damage. Bonechill can also be defeated by using Luigi's Super Jump technique below his head.
Names in other languages