Gloomtail

"Quake in fear, mortals! For I am Gloomtail!"

- Gloomtail

Gloomtail is the middle sibling in the "tail" family in Paper Mario: The Thousand-Year Door. He is the older brother of Hooktail and the younger brother of Bonetail. Upon hearing Mario's partners say they defeated his sister Hooktail, Gloomtail vows to destroy Mario and company, because he hates it when anybody messes with his sister. He lives in the Palace of Shadow and guards the Star Key, which is needed to unlock the pedestals in the Riddle Tower. Mario and company had to defeat Gloomtail to get the Star Key.

Gloomtail is much stronger than his sister. He attacks by breathing poison on Mario and his partner and stomping and chomping the character in front. His Earthquake can hit Team Mario hard, but that attack doesn't work on Vivian and Flurrie. He can also charge up for his signature and strongest attack: his famous Megabreath move, which does up to 16 damage, so it is recommended to use Vivian to hide the party, or Boo's Sheets to avoid a load of damage.

Quote
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Trivia

 * Gloomtail is the only dragon boss in Paper Mario: The Thousand-Year Door that does not have a Super Paper Mario equivalent.
 * As with his sister, Gloomtail bears a slight resemblance to the Czar Dragon.