| Paper Mario: The Thousand-Year Door Enemy
| Max HP
|| Palace of Shadow
|| Hooktail's brother. He's a big, dark, poison-spewing baddie. Watch out for his famous Megabreath attack!
|| Poison Breath (8, Poison), Stomp (8), Chomp (8), Earthquake (10; useless against Vivian and Flurrie), Charge +8 (warning for Megabreath), Megabreath (16)
|That's Gloomtail. I think he's Hooktail's brother. I see the family resemblance... He'll bite or stomp you, and he may also breathe poison on you. Great. When his HP gets low, he may throw in some other attacks as well. Wouldn't surprise me. Especially watch out for his megabreath move, 'cause the word is, it's GNARLY! He also stores power for some attacks, so use Vivian to hide to avoid those.
99 100 101
“WHAAAAAAAAAAAAAAAAT?!? You destroyed my precious younger sister?!? I wondered why she hadn't written recently…”
—Gloomtail, Paper Mario: The Thousand-Year Door
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. 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 move can hit hard, but it 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.
For a full list of quotes, see here
 Names in Other Languages
||Taken from the Japanese Bunbaba, but with the M before B because, in Spanish grammar, N should not come directly before B.
||Portmanteau of "toxique" (toxic) and "croc" (fang)
||Portmanteau of "Lohe" (blaze) and a male name like "Robert", "Hubert" or just "Bert"
- Gloomtail is the only dragon boss in Paper Mario: The Thousand-Year Door that does not have a Super Paper Mario equivalent.
- The room Sir Grodus is fought in is directly below Gloomtail's room, which would mean that Bowser was in Gloomtail's room when he fell through the floor.
- Bonetail has the same default attack and defense stats as Gloomtail.
- Gloomtail's room is similar to the spike room in Hooktail's Castle; if the player uses Bobbery at the right end at the wall, a room will open and an Ultra Shroom and a Jammin' Jelly can be collected.
- Gloomtail has the third strongest enemy attack in the entire game. His Megabreath can do 16 points of damage, 2 points higher than the Shadow Queen's Megawave attack. However, if the Shadow Queen charges up (Increases attack and defense) and then charges up for the Megawave, her attack does 17 points of damage. The strongest enemy attack belongs to the Amazy Dayzee, with a power of 20.