Yveltal debuted in An X-cuse to Come Out and Play. It, along with Xerneas, first appeared in Vaniville Town, where they began battling each other. Their clash caused much destruction, forcing the townspeople who lived there to run away in order to escape from harms way. The two Legendary Pokémon were sought after by Team Flare, who intended to use one of them to power their ultimate weapon. After some time, Yveltal and Xerneas stopped fighting and disappeared. With their influence over the media, Team Flare reported that the destruction was caused by a large explosion.
While Team Flare found Xerneas and managed to take it to their secret HQ to power the ultimate weapon, Malva went underground where Yveltal was sleeping and managed to obtain it. Malva revealed her capture of Yveltal at Geosenge Town in Rhyhorn Charges, having it attack Xerxer. Xerosic stops the battle, telling Malva the two are evenly matched and will result in an endless battle.
In Yveltal Steals, after learning where Team Flare had gone into hiding, Y and her friends traveled to the Pokémon Village in order to stop the villains. On their way, Blue was attacked by Yveltal, which had appeared without Malva. Just before Yveltal's attacks could hit Blue, he was saved by Y, who had Xerxer block the attack with its horns. Xerxer told Y and the others to go on ahead to the village while it stayed behind to fight with Yveltal. Although worried that Xerxer may be at a disadvantage due to its weakened state, Xerxer assured Y and her friends that it would be fine.
Later, after Trevor, Tierno, and Shauna finished their battles with the Team Flare scientists, they found that Xerxer and Yveltal were still in battle, but had stopped moving. Xerxer told everyone that Zygarde is the protector of Kalos's ecosystem, which was threatened due to it and Yveltal clashing with each other. It also explained that by it and Yveltal reverting to their dormant tree and cocoon forms, Zygarde would have no reason to stay. As it and Yveltal finished turning to their dormant forms, Xerxer bid farewell to the Vaniville children.
Yveltal appeared in a flashback in PASM30, where Samson Oak discussed how Zygarde appeared to confront it and Xerneas, leaving for Alola once things were settled.
Personality and characteristics
Yveltal is a very powerful Pokémon, easily destroying an entire town in its fight against Xerxer. It seems to hold little regard for anything other than its relationship with Xerxer, though it did listen to its Trainer before returning to its cocoon form. It is also wary of Zygarde, being neither a friend or a foe.
It is capable of draining the life energy from living things and rendering them unable to move. It can also choose to revert to its cocoon form if exhausted.