Xerneas in Pokemon Legends Z-A can be found after completing the main story. It is one of the box legendaries from the original Kalos games. As a Fairy-type with strong Special Attack abilities and a broken signature move, Geomancy, it is a creature you would want on your team for post-game adventures.
This article covers everything you need to know to acquire Xerneas in Pokemon Legends Z-A.
Disclaimer: This article covers post-game information.
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Steps to get Xerneas in Pokemon Legends Z-A
After the credits roll, you must take part in the Infinite Z-A Royale. For the first quest, you must collect 50,000 points to earn your first Challenger's Ticket. Take this to Quasartico Inc. to challenge Zach. The battle should be a breeze, and once you win it and leave the battle area, you will get a call from Lida to visit Hotel Z.
Lysandre will be at Hotel Z. He will speak to you about Xerneas and Yveltal. Here you must choose between "The One That Gives" and "The One That Takes." After some conversation with your friends, Main Mission 40: The One That Gives kicks off.

After this, go to the Pokemon Research Lab and speak to Mable. Asking her about Xerneas reveals the locations of some Alpha Pokemon in Wild Zones 3, 5, and 9.
In Wild Zone 3, you will encounter a Level 70 Alpha Steelix. In Wild Zone 5, you'll find a Level 70 Alpha Gallade. A Level 70 Alpha Pangoro awaits you in Wild Zone 5. You can either catch them or defeat them to complete the mission.
Once you have covered all three creatures, return to Mable and she will ask you to go to Wild Zone 11 to find Xerneas. Heal your Pokemon and stock up on Ultra Balls before you fly to the area.

Don't enter the Wild Zone where you teleport. Instead, walk up the stairs behind you, take two lefts (you will pass a Galarian Stunfisk and a Tyranitar on your way), and you will see another gate that takes you to the riverfront. Follow the mission marker to trigger the Xerneas encounter.
From here on, you must fight and catch Xerneas to add it to your collection. This will also bring Main Mission 40: The One That Gives to an end.
Also read: Pokemon Legends Z-A Pokedex
Tips to catch Xerneas in Pokemon Legends Z-A
Xerneas knows Geomancy, Megahorn, and Moonblast when you encounter it. Therefore, a Steel-type like Mega Lucario or Mega Excadrill is best suited to fight it. You could also go for a Poison-type like Mega Scolipede. Mega Victreebel can also be effective as it can put Xerneas to sleep or poison it.
Use a Quick Ball to start off the encounter. But later into the fight, use only Ultra Balls for the best chance at catching Xerneas in Pokemon Legends Z-A. Check out how to get all Poke Ball types in Pokemon Legends Z-A.
You can also check out the list of available items and new Mega Evolution stats.
🚨 Calculate how strong your evolved Pokémon will become with our newly launched Pokemon GO Evolution Calculator 🚨