Nihilego TF

A puddle of nihilego poison the user finds in alola. If the user gets too close, the poison will jump at them and transform them into a nihilego Nihilego is an Ultra Beast that resembles a jellyfish. The bell is semi-translucent and encircled with several white, star-shaped markings. The wavy rim of the bell flares outward and is bright blue. Its tentacles appear gelatinous and give it a vaguely humanoid shape. Several tentacles mesh together forming the appearance of a cape or long hair, while four shorter tentacles resemble shorter hair and arms. Two long tentacles make up the legs of the human shape. According to its concept art, Nihilego's body is made of various types of glass.

Nihilego was one of the first Ultra Beast discovered by Professor Mohn for the Aether Foundation. Nihilego live in another world named Ultra Deep Sea, occasionally being brought to Alola through Ultra Wormholes. Although its exact levels of intelligence are unknown, it is believed to act upon a self-preservation instinct, and displays a lack of emotion or even will. However, in addition to its constantly changing human-like shape, it is sometimes seen acting like a young girl. According to Wicke from the Aether Foundation, Nihilego's most distinctive feature is its parasitic capability. When Nihilego latches on to a host's head, it does not manipulate its actions directly. Instead it awakens the host's own capabilities and boosts them to an extreme extent in order to protect itself. It injects the host with a sort of neurotoxin to achieve this effect. This neurotoxin of Nihilego's is incredibly stimulating and inspires feelings of extreme excitement and a lack of inhibition in its host. Anything or anyone that Nihilego latches on to will have its native skills forcibly activated to their fullest extent and will then act as it naturally desires to. Pokémon Adventures also elaborates upon Nihilego's neurotoxin, explaining that its venom turns their negative emotions into happiness and pleasure. It's also said that Nihilego mostly feed on those who feel intense worry or anxiety.

Wicke also claims that like all Ultra Beasts, Nihilego stores Z-Power, the same energy possessed by Totem Pokémon, within its body, which takes the form of a red, flaring aura. As seen in the games, Nihilego are capable of creating illusions, such as making itself and its allies vanish. In The Homecoming Crown!, a Nihilego was shown using its powers to see the memories of people and even alter their perception. That same episode also showed that Nihilego can demonstrate emotions other than self-preservation and the ability to heal people.