To obtain Yveltal in Pokémon games, you typically need to progress through the storyline of Pokémon X or Pokémon Omega Ruby, where Yveltal serves as the version-exclusive Legendary Pokémon. In these games, you will encounter Yveltal in the story at the Tower of Mastery after defeating the Elite Four. To catch it, weaken it in battle, then use Ultra Balls or other Poké Balls to capture it. Ensure to save your game before the encounter, as it can be a challenge to secure its capture.