"Gardevoir has the ability to read the future. If it senses impending danger to its Trainer, this Pokémon is said to unleash its psychokinetic energy at full power, and has the ability to distort the dimensions and create a small black hole. This Pokémon will try to protect its Trainer even at the risk of its own life."
Ralts was given to Lexi by Diantha in Lumiose City following the latters defeat to the former, given a Gardevoirite to hold. She joined Lexi's team and remained with her throughout the conclusion of her initial Kalos journey, remaining outside its Pokéball with Lexi.
Upon Lexi's venture to Hoenn, she personally asked Ralts to remain with her.
Arriving in Hoenn, Ralts began to want to improve herself, becoming more outgoing and showing willingness to battle more. Upon arriving in Slateport City, She was captured alongside Lexi and her friends and taken to the Oceanic Museum, unable to defend herself or the others from Team Aqua. Despite this, when Team Aqua threatened to hurt Lexi so she couldn't continue her journey, Ralts evolved into Kirlia and freed them all.
Kirlia's strength continued to grow as she continued to train and be used in battle. She evolved into Gardevoir in Dig! Dig! Dig! in Rusturf Tunnel after helping defeat the various Pokémon causing the cave to partially collapse.
Finally in her final form, Gardevoir was able to Mega Evolve with the use of the Gardevoirite she continued to hold from Diantha. Gardevoir struggled at first with the new power, however, she was able to control herself using the Psychic-type powers she held and the willingness to control it due to the current threat in Hoenn.
In the words of Diantha, Ralts is very powerful with untapped potential, but is painfully shy around people and Pokémon, opting to hide on Lexi's shoulder most of the time. When it comes to battling, Ralts seems to dislike battling, but is reciprocal towards helping Lexi, becoming quite surprised of its power upon using it. As a Kirlia, she found her passion for battling and protecting both Lexi and her other Pokémon. Finally as a Gardevoir, she became a mother figure for other Pokémon and her mental strength is unmatched compared to others on Lexi's team.
Gardevoir has futuresight; She can sense impending danger to Lexi and will unleash her psychokinetic energy at full power. This power has the ability to distort the dimensions and create a small black hole.