|Home world:||Planet Earth (U40 Timeline)|
|First appearance:||The☆Ultraman episode 5 "The Passenger! Break through the Underground"|
|Affiliation:||Tough Gillan (Mate) Tough Gillaco (offspring)|
Subtitles: Underground Monster (地底怪獣 Chitei Kaijū?)
- Height: 96 m
- Weight: 80,000 t
- Location: Japan Alps
Living in the Japan alps, Tough Gillas was discovered underground using a Subterrene. She then came out and destroyed the vehicle so she could mate with her husband. TBA
Powers and Abilities
- Burrowing: Tough Gillas can burrow at high speeds while underground.
- Neck Quills: Tough Gillas is armed with quills on the back of his neck.
- Extraordinary Jumper: Tough Gillas can jump far into the air.
- Spiked Tail: Tough Gillas can use his tail to bash and flip foes high into the air.
|The☆Ultraman Kaiju & Seijin|
|Seagra | Spiral | Wanigodon | Red Smogy | Tough Gillan | Tough Gillas | Tough Gillaco | Firebadon | Combugon | Robot No.101 | Alien Baltan IV | Mikonos | Dolfiego | Xalome | Hectore | Liquid Monster | Opt | Garadoras | Xyclon | Gellon | Gadon | Goglan | King Moa | Badan | Islanda | Gerada | Janyur | Bedoran | Bader Group | Bagon | Janyur III | Zaanmoth | Zanba | Dragodos | Death Balan | Gibaaroga | Red King | Aboras | Banila | Earthtron | Ghostron | Gokinezula | Alien Baladon | Dabaran | Jadan | Jagon | Skeldon | Garbados | Megasaura | Babilar | Gamiba | Imedo Being | Goadarion | Jinario | Groteng | Plazoon | Agujon | Deathpower | Zuma | Gurol | Darantulas | Alien Noa | Heller | Roygar | Panther | Heller Army | Gumons | Hell Cat | Orolan | Gilos | Gilo | Fake Ultraman Joneus | Hatari | Large Battleship | Dostony | Spader | Caperadon | Alien Scien | Golding | Gedon | Hella Umaya | Heller Fleet | Makdatar|