The One That Gives: 040 2

After completing the main story and one reward match of the Infinite Z-A Royale, you will receive an urgent phone call from Lida.

Head back to Hotel Z to meet L, who will give you Main Mission 40 and Main Mission 41.

Go to the 3F of the Pokémon Research Lab and speak with Mable. She will assign you a research task to deal with three anomalous alphas in different wild zones.

In Wild Zone 3, locate the Level 70 alpha Steelix near the center. This Steel is a Ground-type Pokémon. It can use Stone Edge, Dig, Earthquake, and Double Edge. You can either KO or catch it. Special attackers are recommended, but tanky Pokémon are also useful.

In Wild Zone 5, find the Level 70 alpha Gallade at the west park. This Psychic/Fighting-type Pokémon knows Swords Dance, Psycho Cut, Leaf Blade, and Stone Edge. Pokémon with high Defense or the move Reflect are recommended. You can KO or catch it. Wild Gallade can also be found in Wild Zone 20, or you can evolve one.

In Wild Zone 9, atop a roof at the south-west corner, find the Level 70 alpha Pangoro. This Fighting/Dark-type Pokémon knows Focus Energy and Poison Jab. You can KO or catch it. Wild Pangoro can also be found in Wild Zone 20, or you can evolve one.

Once you have dealt with all three alphas, return to Mable at her lab.

Mable will then instruct you to visit Wild Zone 11.

On the north side of Wild Zone 11, wait for Xerneas to appear.

Xerneas is a Level 75 pure Fairy-type Legendary Pokémon. It can use Geomancy (which boosts Sp. Atk, Sp. Def, and Speed), Moonblast, Horn Leech, and Megahorn.

To counter Xerneas, use Steel or Poison-type Pokémon to resist its Moonblast, especially after Geomancy boosts.

Your objective is to capture Xerneas. If you knock it out, you will have another chance, and it has a fairly high catch rate.