Details: After catching both Xurkitree, return to the Route 8 hotel and report back to Anabel and Looker. Once again, Anabel will inform you that Wicke now has all the details on Xuritree. It is then that Kahuna Nanu returns and tells you that more Ultra Beasts have been spotted on Ula'ula Island, so Anabel suggests meeting back up on Route 13.
Once there, Nanu will further describe how the Ultra Beast Celesteela has been been spotted in the nearby area. But there won't be just one Celesteela, the Flying/Steel Type Pokemon, that needs captured, but a grand total of two of them. They can be found in the Haina Desert and in the Malie Garden.
Both of the Celesteela will be at Level 65, each knowing the Moves of Autotomize, Seed Bomb, Skull Bash, and Iron Defense. Immediately as each Battle with Celesteela begins, like all other Ultra Beast encounters, its highest Stat will be doubled, which is none other than its already incredible Defense Stat. Its highest stat will then increase each and every Time it knocks out one of your Pokemon, per its Beast Boost Ability. Celesteela is exclusive to Pokemon Moon.
After catching both Celesteela, return to Route 13 to tell Anabel and Looker.