This article is incomplete. Please feel free to edit this article to add missing information and complete it. Reason: Missing Ariados's Ability and overworld model, missing information about subsequent battles
Guzma first appears in Malie Garden, taunting Professor Kukui, calling both the professor and himself "fellow rejects who never could become captains." Guzma then criticizes Kukui's idea of building a Pokémon League for Alola. While he agrees that some parts of the island challenge are antiquated, he claims there's no need for a League, as he believes he's the strongest Trainer in the region. To solidify his position, his Grunts have been stealing every piece of Buginium Z across Alola simply to deny its use to other Trainers.
When Kukui asks the player to battle Guzma, the boss takes notice of their Z-Ring, and asks why they're taking on the island challenge before immediately dismissing it and accepting Kukui's terms. The player wins, and Guzma leaves, saying he'll remember the encounter. The player, in an attempt to retrieve a stolen Yungoos, encounters Guzma again at Team Skull's hideout in Po Town. After the player beats Guzma, he vows to defeat the player.
The player later fights Guzma for the third time at Aether Paradise, after he defeats Gladion. After Guzma is beaten, he lets the player pass,moving into Lusamine's room. After Lusamine opens an Ultra Wormhole,summoning ultra beasts all over Alola, Guzma appears to make sure the experiment was a success. He is then battled by Hau while the player battles Lusamine. No matter what the outcome of this battle is, Lusamine notices that the wormhole is closing, and she and Guzma disappear inside of it.
Later,when the player enters the ultra wormhole for themselves,Guzma is seen,and he tells Lillie and the player that Lusamine has lost the ability to be reasoned with,and talks about how he was possessed by a Nihilego, causing him to feel fear for the first time. After the player defeats Lusamine again, Solgaleo/Lunala transports everyone back to the Altar of the Sunne/Moone where they see Hapu, who instructs Guzma to place Lusamine on her Mudsdale.
After the player becomes the champion of Alola, Guzma goes can be found in his parents house on Route 2, where he will tell the player to come to the Hau'oli City beachfront to battle. After he is defeated here, Hala comes and reprimands Guzma for not being able to recognize his opponents strength. Hala then says that he will "make a fine trainer out of him" to make up for the bad things that he and Team Skull caused. Guzma then walks off, but not before giving the player his lucky charm, a Dawn Stone. He also participates as a Trainer in the Battle Tree.
