Nihilego debuted in a flashback duringA Masked Warning!.Gladion revealed toAsh that Nihilego had attempted to kidnapLillie when she was younger. These events, along withFaba wiping her memories afterwards, lead her to fear touching Pokémon.
Another Nihilego appeared inFaba's Revenge!, when Faba created anUltra Wormhole usingNebby's power. After appearing in theAether Foundation basement laboratories, Nihilego promptly knocked out Faba before reaching out for Lillie. However, she was protected byLusamine, 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.
As such, when Gladion, Ash, andhis classmates came to save her inRescuing 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 using10,000,000 Volt Thunderbolt in10,000,000 Reasons to Fight!, allowing Lusamine to separate from it.
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.
Lillie first appeared inThe Homecoming Crown!, living withMohn in theCrown Tundra. In a series of flashbacks, it was shown that when Mohn wound up at theUltra Deep Sea, Lillie rescued him and took him back to his own world through anUltra Wormhole. It then used its powers to make Mohn see it as his daughterLillie, and proceeded to live with him in a remote house for years. To keep Mohn from regaining his memories and leaving it, Lillie removed all the mirrors in the house and dirtied the windows, preventing him from seeing his own reflection.
Years later, Mohn's real family found Mohn in the Crown Tundra, unable to remember his real relatives. Lillie tried to prevent them from revealing the truth to Mohn, but ultimately, they ended up being grateful towards it for having rescued Mohn. Even once Mohn had regained his memories, the family still invited Lillie to stay with them and join the family as a second Lillie. It accepted the invitation and wascaught byGladion.
Unlike mostNihilego in the series, Lillie is shown to be very caring, as seen when it rescuedMohn and took care of him during the time they lived inGalar. It is also shown to be very protective, being ready to attackLillie andLusamine when it felt they were trying to separate it from Mohn.
Lillie is also shown to have a lonely nature, as it didn't want Mohn to regain his memories, fearing that Mohn would abandon it if he did. InHelping the Hometown Hero!, it showed an interest in battling.
Buzzwole enjoys flexing its muscles, as seen inA Mission of Ultra Urgency!, where it got itself into a show of muscle withKiawe andAsh. This ended up distracting Buzzwole, allowing it to be caught.
Trivia
Buzzwole is the first Ultra Beast to be caught by a main character in the animated series.
Celesteela appeared inRise and Shine, Starship!, where it was found bySophocles while camping out at theBamboo 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 to its home.
Celesteela has an extraordinary amount of determination to return home, as seen inRise 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 inTwirling 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 asKiawe was about to catchXurkitree and began to have a performance battle with it, preventing the Ultra Guardians from catching it. With the Ultra Guardians' Pokémon providing a distraction andAsh's Lycanroc weakening Blacephalon withSplintered Stormshards,Lillie was eventually able to catch it, allowing it to be sent back home.
Blacephalon likes to put on displays, as seen inTwirling 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 inTwirling with a Bang!. The next day, the Ultra Guardians were dispatched to catch it, as it was draining electricity from a power line. Just whenKiawe was about to catch it, however, Xurkitree began a performance battle withBlacephalon, preventing the Ultra Guardians from catching it. With the Ultra Guardians' Pokémon providing a distraction andAsh's Lycanroc weakening Xurkitree withSplintered Stormshards,Lana was eventually able to catch it, allowing it to be sent back home.
Xurkitree likes to put on displays, as seen inTwirling with a Bang!, where it had a competition with Blacephalon to see who could put on the best display. Xurkitree also enjoys absorbing electricity.
Naganadel debuted inThe Shape of Love to Come! inAsh's Poipole's dream. It made its physical debut inThe Prism Between Light and Darkness!, where it encountered theUltra Guardians after they arrived in its home world withLunala's help. After being healed, Naganadeltelepathically told everyone how Necrozma lost its light saving the world from a meteor, causing everything to become a dark and barren wasteland. Afterwards, the Ultra Guardians decided to help restore Naganadel's world by sharing theirZ-Power with Necrozma in order to turn it back to its former self.
InSecuring the Future!, Naganadel helped Necrozma regain itstrue 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 of its kind inPoipole's world, Naganadel acts as a guardian to thePoipole living there, and it cares deeply for their safety. Its caring nature extends to other Pokémon as well, as seen when it offeredNecrozma its Z-Power to aid it in regaining itstrue form. Naganadel also comes of as a little stubborn, as seen when it refused theSitrus Berries offered byMallow, untilPoipole convinced it otherwise.
Naganadel has the ability to usetelepathy, which it uses to communicate with humans in human speech.
Stakataka entered Alola through an Ultra Wormhole at thePokémon 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 byViren, 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 theUltra 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 first appeared inBattling the Beast Within!, where it attackedAsh andPikachu in theUltra Ruin beforeDia and hisZeraora intervened, driving it off. Dia later revealed to Ash that Guzzlord was the cause of the devastation of his home world. InParallel Friendships!, Ash and Dia sent Guzzlord through anUltra Wormhole and back to its home world, with the help of the Shiny Tapu Koko, who made it possible forZ-Moves to be used again in the Ultra Ruin.
Personality and characteristics
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 series, 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.
A Guzzlord appeared inEnter the Champion!, where it emerged through an Ultra Wormhole at the end of theManalo Conference. It reappeared inthe next episode, where it started to attack the stadium, forcing the crowd to evacuate. It almost ateTeam Rocket untilBewear showed up and threw it outside the stadium. Bewear put up a good fight until Stufful fell off its back, when Guzzlord relentlessly attacked Bewear until Team Rocket rescued the two and escaped.
With help from theguardian deities, who prevented it from moving, theisland kahunas were able to hit it with theirZ-Moves and sent it back through its Ultra Wormhole.
TwoShinyGuzzlord appeared inZ-Move Showdown!. They each emerged through an Ultra Wormhole following theManalo Conference. One Shiny Guzzlord confrontedAsh's classmates,Hau, andGladion, but they were able to defeat it by using all of their Z-Moves, which sent it back through its Ultra Wormhole.
Another,giant Shiny Guzzlord attackedProfessor Kukui, disguised as the Masked Royal, andAsh. Professor Kukui attempted to battle it with hisLucario, but it was soon overpowered. Suddenly, aNaganadel 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 twoGigavolt Havocs.
Personality and characteristics
Like other Guzzlord, these two are extremely aggressive and attack and eat anything in their path.
Pheromosa debuted inBeauty is Only Crystal Deep!, where it arrived inAlola through anUltra Wormhole. It started attackingTrainers who possessedZ-Crystals and stole them, eventually building up a collection of them.Meowth later developed a crush on it and prevented theUltra Guardians from catching it. Pheromosa was eventually defeated byBewear, which allowed the Ultra Guardians to catch it and return it home.
Personality and characteristics
Pheromosa's habit of collecting Z-Crystals
Pheromosa likes collecting Z-Crystals, as seen when it went around attacking Trainers who owned them and stealing them, and was apparently charmed by their beautiful display, proudly displaying them to others, both as a way to mock them, and to show off its "jewelry".
Furthermore, Pheromosa is an extremely manipulative and cunning Pokémon, using its good looks and physical appeal to charm other Pokémon into doing its bidding, and once its followers have no further use for it, Pheromosa abandons them without hesitation, seen when Pheromosa charmedMeowth into helping the Ultra Beast collect Z-Crystals, and abandoned him once Meowth got stuck into theUltra Guardians's trap trying to protect it.
Pheromosa is also quite a sore loser, seen as after it was captured byAsh and about to be returned to its homeworld, Pheromosa was visibly displeased at being defeated and captured, sticking out its tongue at the Ultra Guardians before entering theUltra Wormhole.
Kartana debuted inLiving on the Cutting Edge!, appearing inAlola through anUltra Wormhole. It started slicing through various objects acrossMelemele Island, promptingAsh andhis classmates to embark on their eighth mission as theUltra Guardians. Their efforts to catch it ended in failure, and were soon overshadowed by a meteor falling towardsPokémon 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 inLiving 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 generally cuts objects for fun, Kartana does also cut things to help others, as seen where it cut the cabbage atAina's Kitchen and the meteor that threatened to hit thePokémon School (which Kartana noted to be a "good cut.")
Trivia
Kartana's habit to call objects worthless after cutting them might be areference toGoemon Ishikawa XIII fromLupin III, who shares a similar catchphrase ("Once again, I have cut a worthless object.").
Coincidentally, both characters have been voiced byDaisuke Namikawa in Japanese.
Unknown Ultra Beast
The unknown Ultra Beast's homeworld
InThank You, Alola! The Journey Continues!, Ash mentioned meeting an Ultra Beast he had never seen before during a trip in Ultra Space withNebby, with Rotom recording the encounter. However, it was never shown onscreen.
