Clemont's Heliolisk is one of Clemont's Pokémon who is living in the Lumiose City Gym.
Prior to Clemont's journey with Ash and Serena, Clemont raised Heliolisk as Helioptile and evolved it with a Sun Stone.
Clemont lent Heliolisk to Clembot while he was away. When Clemont returned and challenged Clembot for ownership of the gym, Clembot used it to battle. Helolisk lost to Bunnelby.
Prior to Ash's gym battle with Clemont, Heliolisk battled against Tierno and his Squirtle and lost.
Heliolisk was later used in a battle against a crazy scientist named Belmondo and his robotic creation, Black Clembot. Heliolisk fought against Belmondo's Magneton, but the battle was interrupted when Team Rocket showed up and tried to capture both Clembot and Black Clembot. After Blaziken Mask sent Team Rocket blasting off with his Mega Blaziken, Clemont recalled Heliolisk to its PokéBall.
Heliolisk was used as the second Pokémon Clemont chose in a gym battle against Ash. In the battle, Heliolisk fought against Ash's Goodra. Despite Goodra's enormous size and power, Heliolisk weaken Goodra with its speed, using Flash to blind Goodra and Thunder Wave to paralyze it. This causes Ash to recall Goodra and sent out his Hawlucha. Heliolisk managed to weaken Hawlucha with its Parabolic Charge ability, but despite this, Hawlucha successfully defeated Heliolisk with a direct hit from High Jump Kick, giving Ash the second win against Clemont.