Bonechill is the main antagonist in chapter seven in the game Super Paper Mario. He is a gigantic semi-skeletal dragon, who commands the cold, and was after a pure heart in the Overthere (The Mario Universe equivalent for Heaven).
Bonechill was once held below the Underwhere (the Mario Universe equivalent for Hell or the underworld), but was released by an earthquake, and entered the Overthere with several demons called Skellobits (the dead who were evil in life and sent to suffer among the game-overed). He attacked Grambi, King of the Overthere, before Mario, Peach, Bowser, and Luigi arrived to stop him. Bonechill revealed to Luvbi, Grambi's daughter who was traveling with Mario, that she was the eighth and final Pure Heart, turned into a Nimbi (angel) by Grambi and Jaydes (Queen of the Underwhere). Mario, Peach, Bowser, and Luigi fought Bonechill and defeated him. Bonechill was destroyed, shattering to bits.
Bonechill has 80 HP. He can breathe ice to freeze Mario and his allies, and make icicles fall from the ceiling. He also shoots icelike missiles from his cannon. To defeat him, you must grab icicles or missiles using Thoreau, and throw them at his head. Alternately, Luigi's Super Jump can be used to defeat him.