Zamazenta first appeared when Goh was looking through the Slumbering Weald for Pokémon to catch. He came across the Warrior Pokémon and attempted to identify it with his Rotom Phone, though nothing was detected. Goh also attempted to throw a Poké Ball at the illusion Zamazenta and Raboot used Ember to attack the mysterious Pokémon, though the efforts were futile. Zamazenta howled, creating more fog before disappeared without a trace.
While finding statues that depicted Zamazenta alongside Zacian, Goh returned to the Slumbering Weald with Sonia to call for the Legendary Pokémon to help with the suddenly outbreak in rampaging Dynamax Pokémon. While wandering through the thick fog, Zamazenta and Zacian appeared before the two shortly before going back into the fog. Goh and Sonia followed the Legendary Pokémon only to find an altar with the Rusted Shield and Rusted Sword.
Ash and Goh headed to the Galar Power Plant to confront Eternatus, bearing the Rusted Sword and Rusted Shield. Suddenly, the objects began to glow as Zamazenta and Zacian retrieve them, causing them to transform into their Crowned Shield and Crowned Sword forms, respectively. Zacian uses Behemoth Blade and Zamazenta uses Behemoth Bash, helping Ash and Goh defeat Eternatus as Goh throws a Poké Ball at the once Eternamaxed Pokémon, successfully catching it. After the battle, Zacian and Zamazenta leave the scene, leaving behind their weapons.
Ash and Goh visit the altar where the weapons were as Zacian and Zamazenta approach them. Ash hopes to one day battle the strong Pokémon while Goh hopes to catch lots of Pokémon in the future.