Dexio is one of
Professor Sycamore's assistants, first appearing in the Pokémon X and Y games. Both he and
Sina help the player,
Calem or
Serena, through their journeys, upgrading their Pokedexes several times through the games. They also pretend to be superheroes, complete with disguises and a name: Defenders of Kalos.
In the Alola games, they task
Elio or
Selene with helping them out with Zygarde core research.