Go to the motel and Mina will be there, informing Looker of where she saw UB-03 Lighting. You need to battle Mina before taking the task.
After doing it, you get informed it has been spotted in Lush Jungle and Memorial Hill. Again, you need to capture 2
UB-03's Special Attack is boosted by two stages
UB-03 is Xurkitree, an Electric-type. Level 65
Capture both Xurkitree and return to Looker for a job well done, then Nanu comes in. He tells you that UB-04, Blade, is on Ula'Ula island
UB04 is found in Route 17 and Malie Garden and you have to capture 4 of them.
UB-04's Attack is boosted by two stages
UB-04 is Kartana, an Grass/Steel-type. Level 60. In Moon, it is the Steel/Flying-type Celesteela
Capture them all an speak to Looker and he'll explain how 10 years ago he came to Alola to stop Ultra Beasts but Nanu comes in and explains Looker felt sorry for the beast and caused the mission to fall apart and caused one of their team to be lost. Nanu then says the next Ultra Beast is found on Poni Island and to go to the restaurant in Seafolk Village.
When there, they explain how they found Anabel 10 years ago, losing most of her memories. All she knew was she was called Anabel, was from Hoenn, protected the tower and was a powerful trainer and joined the International Police due to wormhole energy. (Sounds a lot like Looker in ORAS)
As you go that path, Dexio and Sina appear and tell you about Mega Evolution
Deep in the cave, you will find UB-05 Gluttony. It is Level 70
UB-05's Attack is boosted by two stages
UB-05 is called Guzzlord, is Dark/Dragon-type. Level 70
Return to the restaurant and Looker & Anabel will congratulate you on a job well done and suggest reporting to Wicke about contianing all the Ultra Beasts.
When you go there, Looker bursts in and informs you of a mysterious black creatured zzipping across the sky of Alola. He insists it's an Ultra Beast but Anabel says there's no word of more Ultra Beasts. They say about how it must be Looker being tired. Anabel leaves to meet Nanu and Looker goes to the motel on Melemele Island
Necrozma can be found roaming around Ten Carat Hill. It's Level 75. Not an Ultra Beast so don't use Beast Balls
When you get to the Battle Tree, Red & Blue appear and challenge you, asking who you wish to battle: Red or Blue
They were called there to be the bosses of the Battle Tree and will appear at the top of it
Thanks to leaks, we knew that if you had the Legendary Pokémon of the game, you could go over to the alt world when it's Night in Sun and Day in Moon in order to make it Day or Night again. However, if you trade over the other legend, you'll be able to do this at the other time so have 24/7 access to the alt world