Quick Scoop

To catch Yveltal in Pokémon Legends: Z-A, you usually need to reach the post- game, clear the required main missions, then complete the Yveltal-related mission chain that sends you to Grisham/Griselle, Vinnie, and the rooftop encounter in the Rouge District.

Steps

  1. Progress to the post-game and unlock the Yveltal mission chain.
  1. Speak with Grisham and Griselle at Café Nouveau, then go to Quasartico Inc. to meet Vinnie.
  1. Defeat the three rogue Mega Evolution fights: Victreebel, Hawlucha, and Tyranitar.
  1. Go to the rooftop area in the Rouge District, climb the scaffolding/ladder route, and interact with the marker on the dome to start the battle.
  1. Battle Yveltal, weaken it carefully, and throw Ultra Balls or Timer Balls while keeping an eye on its attacks.

Catch Tips

  • Bring a strong Fairy-type attacker if you have one, since Yveltal is weak to Fairy.
  • Save before the fight so you can retry if needed.
  • Don’t knock it out too early; lowering its HP and then switching to good Poké Balls improves your odds.

Route In One Line

Post-game unlocks mission chain -> talk to Grisham/Griselle -> talk to Vinnie -> beat the three rogue Megas -> go to the Rouge District rooftop dome -> start the Yveltal battle.

TL;DR

Yveltal is not a wild overworld spawn; you unlock it through the post-game mission chain, beat the required Mega battles, then find it on the Rouge District rooftop and catch it in battle.