Nihilego debuted in a flashback during A Masked Warning!. Gladion revealed to Ash that Nihilego had attempted to kidnap Lillie when she was younger. These events, along with Faba wiping her memories afterwards, lead her to fear touching Pokémon.
Another Nihilego appeared in Faba's Revenge!, when Faba created an Ultra Wormhole using Nebby's power. After appearing in the Aether Foundation basement laboratories, Nihilego promptly knocked out Faba before reaching out for Lillie. However, she was protected by Lusamine, who was captured instead and then taken through the Wormhole. After attaching itself to Lusamine, it started playing on her desires and reduced her mentality to that of a child's.
Lusamine fused with Nihilego
As such, when Gladion, Ash, and his classmates came to save her in Rescuing the Unwilling!, she instead ran away, releasing her Pokémon enhanced by Nihilego's power as a deterrent. Nihilego also used various other means to deter the children, but in the end was cornered by Ash, Lillie, and Gladion. When Lillie managed to get through to Lusamine, Nihilego interfered, trying to keep Lusamine to itself. In the end, Ash managed to defeat it using 10,000,000 Volt Thunderbolt in 10,000,000 Reasons to Fight!, allowing Lusamine to separate from it.
Personality and characteristics
Nihilego is a very hostile Pokémon, attacking anyone on sight and even kidnapping Lusamine. According to Gladion, Nihilego might have an interest in humans, which is why it fused itself with Lusamine; this was an attempt to learn more about them.
Celesteela appeared in Rise and Shine, Starship!, where it was found by Sophocles while camping out at the Bamboo Hill. It actually arrived in Alola approximately 200 years ago in what was believed to be a naturally appearing Ultra Wormhole, and was stuck in the ground ever since, passively absorbing energy for a take off. After it was dug up, Celesteela was discovered by Lusamine's group, who told the Ultra Guardians to go out and catch it. Their attempts to catch it failed, as Celesteela was too deeply rooted to the ground at the time. When they discovered that Celesteela was preparing to take off, the Ultra Guardians realized that the flames produced when it flies would set the surrounding area ablaze. Using their Ride Pokémon, the Ultra Guardians were able to construct a defensive barrier, allowing Celesteela to safely blast off and return back to its home.
Celesteela has an extraordinary amount of determination to return home, as seen in Rise and Shine, Starship!, where it prepared to blast off despite the Ultra Guardians' requests for it to wait until they can form a protective barrier around it.
Blacephalon appeared in Twirling with a Bang! during a fireworks show. Ash and his classmates were amazed by its performance, believing it to be a part of the show.
The next day, they learned that it was actually an Ultra Beast and set out to catch it. Blacephalon appeared just as Kiawe was about to catch Xurkitree and began to have a performance battle with it, preventing the Ultra Guardians from catching it. With the Ultra Guardians' Pokémon providing a distraction and Ash's Lycanroc weakening Blacephalon with Splintered Stormshards, Lillie was eventually able to catch it, allowing it to be sent back home.
Blacephalon likes to put on displays, as seen in Twirling with a Bang!, where it amazed large crowds of people. It is also competitive, as seen when it had a contest with Xurkitree to see who could put on the best display.
Xurkitree appeared in Alola one night in Twirling with a Bang!. The next day, the Ultra Guardians were dispatched to catch it, as it was draining electricity from a power line. Just when Kiawe was about to catch it, however, Xurkitree began a performance battle with Blacephalon, preventing the Ultra Guardians from catching it. With the Ultra Guardians' Pokémon providing a distraction and Ash's Lycanroc weakening Xurkitree with Splintered Stormshards, Lana was eventually able to catch it, allowing it to be sent back home.
In Securing the Future!, Naganadel helped Necrozma regain its true form by giving it some of its Z-Power. Once successful, Necrozma turned back into Ultra Necrozma and restored Naganadel's home world to its former glory. As the Ultra Guardians prepared to leave, Naganadel informed Ash that Poipole wished to stay behind and protect its home, much to Ash's sadness.
Being the oldest in Poipole's world, Naganadel acts as a guardian to the Poipole living there, and cares deeply for their safety. Its caring nature extends to other Pokémon as well, as seen when it offered Necrozma its Z-Power to aid it in regaining its true form. Naganadel also comes of as a little stubborn, as seen when it refused the Sitrus Berries offered by Mallow, until Poipole convinced it otherwise.
Naganadel has the ability to use telepathy, which it uses to communicate with humans in human speech.
Stakataka entered Alola through an Ultra Wormhole at the Pokémon School. The initial attempts by the Ultra Guardians to catch it failed due to it managing to avoid all of their Beast Balls, and during the following night, it moved to a construction site owned by Viren, where it was mistaken for a pedestal for a statue of Viren. Once the statue was placed on top of it, Stakataka became angry and started rampaging around until Ash removed the statue. Stakataka then let itself be caught by Ash upon learning that he wanted to help it get back home. Later, back at the Pokémon School, Stakataka was safely returned to its home dimension through an Ultra Wormhole.
Personality and characteristics
Stakataka is a docile Pokémon who likes to not be bothered, as seen when it refused to be caught by the Ultra Guardians, in favor of resting. It also dislikes having anything on top of its body, and starts rampaging if it is bothered that way. It has a strong desire to return to its home, as seen when it grew teary-eyed when Ash offered to return it to its home, finally allowing itself to be caught for the purpose.
Guzzlord is a strong and ruthless Pokémon, attacking people and Pokémon without mercy, and it is capable of causing mass destruction. Unlike other Ultra Beasts in the anime, Guzzlord resisted being sent through an Ultra Wormhole; it was either unable to understand its significance, or simply refused to return to its home world.
Another, giant Shiny Guzzlord attacked Professor Kukui, disguised as the Masked Royal, and Ash. Professor Kukui attempted to battle it with his Lucario, but it was soon overpowered. Suddenly, a Naganadel that previously belonged to Ash arrived through its own Ultra Wormhole. Professor Kukui and Ash were then able to send the Guzzlord through Naganadel's Ultra Wormhole with two Gigavolt Havocs.
Pheromosa likes collecting Z-Crystals, as seen when it went around attacking Trainers who owned them and stealing them. Pheromosa is also cunning, as seen where it used Meowth's affections for it to its advantage when the Ultra Guardians attempted to trap it with glue.
Kartana debuted in Living on the Cutting Edge!, appearing in Alola through an Ultra Wormhole. It started slicing through various objects across Melemele Island, prompting Ash and his classmates to embark on their eighth mission as the Ultra Guardians. Their efforts to catch it ended in failure, and were soon overshadowed by a meteor falling towards Pokémon School. Unexpectedly, Kartana sliced the meteor to small, harmless pieces before it could hit the building, saving the school. Afterwards, it created itself a new Ultra Wormhole by repeatedly slicing the air in rapid succession, allowing it to return itself home.
Personality and characteristics
Kartana enjoys cutting through objects at random, as seen in Living on the Cutting Edge!, where it went on a cutting spree. It considered most of the objects it cut through to be worthless. Although it did it for fun, Kartana does it to help out, as seen where it cut the cabbage at Aina's Kitchen and the meteor that threatened to hit the Pokémon School.