Alva evolved Gengar into Mega-evolved state and had it use Psychic on Volcanion when the latter approached them to take Magearna with itself. It alongside Levi's Glalie and Alakazam used their respective attacks on Volcanion, only to be intercepted by Ash's Pokémon.
Upon Alva's order, Gengar used Mean Look on Magearna, which enabled Alva to take Magearna's Soul- heart. It threw Magearna off the aircraft and used Hypnosis on Raleigh. Later, it battled against Volcanion, Ash's Pikachu and Greninja, but escaped after Ash broke the device which allowed Alva control over it.