Stow-on-Side Stadium is the largest building in the town and is the site at which the fourth installment in the Galarregion's Gym Challenge takes place.
During the Gym mission, the player has to navigate sloped mazes while inside a spinning teacup. There are three courses in total.
The teacup naturally slides downwards, but the player can influence its movement by rotating the Control Stick in the direction they want the teacup to spin. Hitting a wall or obstacle can cause the teacup to lose momentum, but does not otherwise penalize the player. In the second and third course, there are several boxing glovesSw/ghoulish handsSh on springs against the edges of the course that launch the teacup away when it comes into contact with them.
At the end of each course, the player has to battle a Gym Trainer. Behind each Trainer is a warp tile that the player can use to return to the entrance, from where they can withdraw from their Gym Challenge. After completing three courses, the Gym mission is complete.
The player can withdraw from the Gym mission at any time by returning to the entrance. If the player loses a battle or withdraws, the mission is reset; however, defeated Gym Trainers cannot be battled again. Once the player has completed the Gym mission, even if they leave or lose, they proceed straight to the Gym battle from the reception area.
In The Winding Path to Greatness!, Ash and Goh visited Allister's Ghost-type Gym in Stow-on-Side to get his help in getting Ash's Gengar to Gigantamax. Allister accompanied them to the Stow-on-Side Stadium, where Bea allowed them to use the stadium battlefield for their training. When it turned out that Gengar could only perform standard Dynamax, Allister assisted Ash and Goh in collecting Max Mushrooms to make Max Soup, which enabled Gengar to Gigantamax when Ash attempted it again.
Pokémon used in the Gym
Grapploct is Bea's first known Pokémon. In Battle Three With Bea!, it was the first Pokémon Bea used in her second rematch with Ash. It first went up against Pikachu, who was soon switched out for Lucario. After a while, Grapploct was recalled and replaced with Hawlucha. In the next episode, it was sent out to battle Ash's Pikachu, defeating him before being knocked out by Lucario.
Machamp is Bea's ace Pokémon, being capable of Gigantamaxing. In Battle Three With Bea!, Machamp was the third Pokémon Bea used in her second rematch with Ash, being sent out to battle his Lucario. In the next episode, it fought against Ash's Sirfetch'd after Lucario had been recalled, before being recalled itself. It was later sent out to battle Ash's Pikachu, defeating it before facing Lucario again. In response to Ash's decision to Mega Evolve Lucario, Bea Gigantamaxed Machamp. Lucario managed to survive long enough for Machamp to revert back to normal, and then proceeded to defeat it soon afterwards, making Ash the winner.
In Shocking!! Reunion in the Forest, it was revealed that Allister and Bea take turns in leading the Gym and taking on Gym Challengers. In PASS18, Marnie revealed that, due to Allister having left the Gym after his battle with Casey in order to follow Casey and her friends, she had been forced to battle Bea instead. She had managed to defeat Bea and win herself the Fighting Badge, despite her Morpeko being at a disadvantage against Bea's Fighting Pokémon.
Gengar is Allister's third known Pokémon. It was first used in Allister's Gym battle against Henry, but was defeated by his Gunbain after its Gigantamax wore off. Allister also uses it as a mode of transportation. It is housed in a Dusk Ball.