Bonetail is a boss character in Paper Mario: The Thousand-Year Door for the GameCube. He is the final boss in the Pit of 100 Trials, one of the sidequests in the game. He has two siblings, Hooktail and Gloomtail. Bonetail is the oldest of the three siblings. He is a skeletal dragon who is the strongest enemy in the entire game. One of the game's characters explains that Bonetail was once a pet to the Shadow Queen, and was put in the Pit of 100 trials so that any one that enters the area will be punished by death. He has a whopping 200 HP. As the hardest boss in the game, take him seriously.
Once Mario will defeat the powerful boss, he will obtain the outstanding Return Postage badge.