The player can use the Zygarde Cells and Cores that they collect in the Zygarde Cube with a Reassembly Machine on Route 16 on Ula'ula Island to create different Zygarde forms. The player can create multiple Zygarde if they have the right amounts of Zygarde Cells and Cores.
The Reassembly Unit will always use the maximum amount of Cells and Cores it can in assembly operations.
If Zygarde is assembled completely from Cells and Cores from the Zygarde Cube, its level depends on whether the player has become the Champion. Before the player has become Champion, assembled Zygarde will be level 30, but after, they will be level 50.
After becoming Champion, the player and Lillie visit Tapu Koko's shrine at the Ruins of Conflict to thank it. Tapu Koko will then challenge the player, acting as the final battle the player has before the credits roll. If Tapu Koko is defeated without capturing it or fled from, it will respawn after the player successfully defends their title.
After the credits, the player can challenge the other three guardian deities.
After becoming Champion, if the player visits the Route 8 motel on Akala Island, they will be recruited by Anabel and Looker to capture the Ultra Beasts that escaped from the Ultra Wormhole as a form of protective custody. There are five different missions to capture different Ultra Beasts that will take the player to each of Alola four islands. In some missions, there will be multiple of the same species, and in some missions, the Ultra Beast may be able to be found in either of two locations.
When a battle with an Ultra Beast begins, it will be surrounded by an aura that sharply increases one of its stats. To help capturing the Ultra Beasts them, the player is given ten Beast Balls at the start of each mission. Most Poké Balls except the Master Ball and Beast Balls are no more effective than a regular Poké Ball against Ultra Beasts. The Beast Ball, however, is specifically designed to overcome this limitation.
If the player flees from or defeats any of the Ultra Beasts, they can still be found again immediately at the same place (or the alternate location, if applicable and if so desired).