During the Gym battle against Ash Ketchum, it faced off against Ash's Fletchinder in the first match up. Valerie talked to her Sylveon in Pokémon language and it was able to more or less understand what she wanted to do. Valerie's Sylveon being a Fairy type is delicate but strong. It used its tail ribbons to its advantage during the battle to capture Ash's Fletchinder from moving about but he countered that but charging right into Sylveon with Flame Charge. The battle came to a climax when the two charged at each other with Giga Impact and Steel Wing but Ash's Fletchinder came out victorious and knocked out Valerie's Sylveon to win the first match-up.
Ash's Talonflame is the evolved form of Ash's Fletchinder. It evolved during a battle against Moltres at Mount Ardor. An attack was heading towards Ash Ketchum and the others and in a burst of adrenaline to go protect them, it also triggered it to evolve.