Lysandre sent Gyarados to intimidate Tierno, Shauna and Trevor, wanting to see pictures Trevor took in Vaniville Town. Fortunately for the kids, Diantha arrived with her Gardevoir, claiming Lysandre has frightened the children too much. Later on, Lysandre was called for an important meeting and went off with Gyarados, claiming it was "one of the chosen ones".
After X infiltrated the Team Flare headquarters, he faced Lysandre. Lysandre showed him Korrina's Key Stone on the ring he wore and touched it, starting to Mega Evolve Gyarados.
None of Gyarados' moves are known.