Malva used her Houndoom in her battle against Alain and his Mega Charizard. Mega Charizard used Flamethrower on Houndoom but it was unaffected by it due to its Flash Fire ability. Malva then Mega Evolved her Houndoom into Mega Houndoom. It used Flamethrower on Mega Charizard and it was trying to block it, but it was overwhelmed by its strength. Mega Houndoom then used Smog which was able to hit Mega Charizard. Mega Charizard used Steel Wing and Mega Houndoom was able to stop the attack and threw Mega Charizard on the ground by using Crunch. Mega Charizard used Flamethrower to throw Mega Houndoom from it, which it was successful in doing. Mega Houndoom then used Dark Pulse but was countered by Mega Charizard's Dragon Claw and Mega Houndoom countered Dragon Claw by using Crunch. Both it and Mega Charizard then used Flamethrower, which collided with each other. Malva then ordered Mega Houndoom to finish Mega Charizard off by using Crunch but Mega Charizard roared and used Blast Burn. Blast Burn overwhelmed Mega Houndoom and the attack knocked Mega Houndoom out, transforming back to its normal form. Alain and Charizard won the battle and Malva recalled her Houndoom, saying that it did a great job.
Malva had Mega Houndoom stop Lysandre's Mega Gyarados' Hyper Beam attack. Lysandre was surprised, though Malva admitted she didn't support Team Flare's goals. After Lysandre was defeated, Mega Houndoom reverted back to its original form. Malva later used Houndoom to assist in the fight against the Giant Rock. Malva and Mega Houndoom joined the fight to thwart away the sprouted plants. Mega Houndoom used Flamethrower to stop the plants before Malva was pulled away by the plants, along with Professor Sycamore. Once Chespie was rescued, Mega Houndoom launched an attack at the Giant Rock, which fused with others' attacks to destroy it. Along with its trainer, Houndoom watched as Zygarde destroyed the Giant Rock and defeated Lysandre.
Ash remembered Malva and her Houndoom fighting the Giant Rock with the rest when he was reflecting back on his journey.