"To think to overwhelm him with sheer mass, I'm impressed!"
"I know it's cheap to scale up, but our guest is being cheap too. You're up, Gridman. How will you fight a Kaiju of this size?"
- ―Alexis and Akane
Subtitle: Monster of Many Difficulties (多事多難怪獣 Tajitanan Kaijū)
Akane was getting fed up of Gridman defeating all her kaiju, so she decided to try creating one that would dominate him using great size. Go'yavec was brought into action by Alexis when Akane called him during her rafting trip, having confirmed her suspicions of Yuta Hibiki transforming into Gridman. Go'yavec then caused aimless destruction and started a forest fire, endangering the Tsutsujidai students and staff. This went on for a while, disappointing Akane who expected Gridman to show up sooner. After Rikka Takarada called her mother's shop, the Neon Genesis Junior High Students bought Junk using whatever money they could fork up and brought it all the way to near the forest area, allowing Yuta to Access Flash and fight Go'yavec. Buster Borr joined the battle was well, providing support to Gridman against Go'yavec and Anti, who had joined the battle. Combining into Buster Gridman, the Twin Buster Grid Beam was used to destroy Go'yavec, whose remains crumbled over Anti.
Go'yavec was the last of the Kaiju army summoned by Alexis, and it almost defeated Gridknight. Luckily, Full Powered Gridman arrived in the nick of time to protect Gridknight and the gigiantic monster was finished off the same was as before - with the Twin Buster Grid Beam.
- Designer: Osamu Yamaguchi
- The monster's huge mouth may have been inspired by Scylla, while the rest of its design and abilities may have been inspired by Volcadon or Zumbolar.
- Unlike the rest of the Kaiju so far, Go'yavec does not have a 3D animation model, but is rather animated as if it were a part of the scenery and background instead. As a result, its movements were stiff and limited.
- Powers and Weapons
- Fireballs: Go'yavec can erupt fireballs of great power from its back.
- Claws: Each of its claws is very large and can be used to attack with.
- Size: Go'yavec's main weapon is its gigantic mountain-sized body, which is too huge for Gridman to attack normally. The monster is so large that Gridman is barely the size of its nail.
- Durability: Its entire body is covered in a rock-like outer layer that protects it from damage, but is useless against heavy firepower.