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.