Challenge from Underground (地底からの挑戦 Chitei kara no Chōsen) is the twenty-first episode of Ultraman Max.
Strange monsters, identified as Gomorasaurases, are spotted. A female reporter believes they are smuggled in by an organization developing bioweapons. She leads DASH to where she believes a monster nest is...
Some hikers find a mysterious upheaval, and videtape it. A monster breaks out: a small Gomora. The news picks it up. They interview a reporter, a woman named Kanami, who believes an organization called GSTE smuggled five gomorasaurases to Japan before they disappeared. She believes the organization is hiding in the area, developing biological weapons to wipe out modern society.
DASH investigates and believes there must be a nest. Kanami says she will guide them to it. She tells them the smuggler is her father, an expert in bio-engineering. She tells them GSTE is an organization called God Save The Earth, a group that extorted corporations and blew up buildings. Just then, the captain and Kanami are trapped when the ground underneath them gives way. Koba and Sean investigate from above.
The captain and Kanami waken in a cave. A magnetic field prevents communication. Elly detects a monster, and Gomora rises above ground. DASH manages to drive it off. Meanwhile, the captain and Kanami manage to find an underground GSTE base. It is abandoned. She finds a record of how all the members died one by one, as her father, Uno, worked on his bioweapon.
The two are attacked by a small Gomora, but manage to escape the lab, which is destroyed. The giant Gomora arrives above ground, while Hijikata and Kanami do as well. Kaito is taken down, but manages to transform into Ultraman Max. He destroys the monster using the Max Galaxy. Kanami intends to prove the connection between the GTSE and Fridnya, the country the gomorasaruses were smuggled from, in the end.
- Ultraman Max Volume 6 features episodes 19-22.
- Ultraman Max Complete Season.
- Telesdon was originally going to appear, but was replaced by Gomora for unknown reasons.
- The Ultraman Orb episode, The Lord of Earth, features an easter egg to this episode. The title was said by Shin Matsudo of SSP when they are trying to hypothesise what could have created the sinkholes in the city.
- The episode was premiered in the United States on TOKU on March 13, 2017