Wally is a Trainer who grows in the hope of catching up to you. This shy young man lives with his parents in petalburg City. Wally rarely speaks and takes care to be polite, giving him the impression of being a meek child. Ralts is first Pokemon he ever caught and becomes his partner.
As they both grow stronger, Wally will become a Mega Evolution user himself. Capable of transforming his Gallade to Mega Gallade through his Mega Pendant, he will prove to be a worthy rival.
Source: pokemonrubysapphire.com