Nanika

Nanika is a mysterious Dark Continent creature who came to possess Alluka Zoldyck under unknown circumstances. The two currently coexist inside Alluka's body. Nanika's real appearance is unknown. When it manifests itself, it tinges Alluka's sclerae, irises, and mouth pitch black, also causing the latter to appear larger. Like Alluka, Nanika is very fond of Killua Zoldyck, whom it fondly calls by name. Nanika strives to earn people's praise and especially Killua's by granting wishes and usually asks him to pet it. When Killua orders it never to appear any longer, Nanika becomes hurt and cries. It later forgives Killua, after Killua promises to protect both Alluka and Nanika and to pet Nanika whenever it wished. Nanika also appears to be on good terms with Alluka, as the latter was very upset when she felt its misery. It is unknown when and how Nanika came to possess Alluka, but the two have shared the latter's body at least since Alluka was a young child.

The Zoldyck Family is in the dark about Nanika's nature. Killua once saw Alluka turn into Nanika, and learned about the general nature of its abilities by asking it how to revert the transformation. As a toddler, Alluka once asked Mitsuba, an attendant of the Zoldyck Family, to do three simple things: carrying her, going up a staircase, and raising Alluka up in the air. After Mitsuba did what she was told, Alluka's eyes and mouth suddenly turned pitch-black. Freaked out by this, Mitsuba called for help. Killua came and changed Alluka back to normal by asking Alluka to make himself go "high-high", which Alluka did. After the accident, Killua had to tell his parents about Alluka's secret because Mitsuba had already reported it to them. It turned out that when Alluka had three requests fulfilled, her eyes and mouth would turn pitch-black, and they would change back to normal only when she heard and granted a wish. Alluka in wish granting mode as a toddler To test the ability, her mother Kikyo Zoldyck ordered Mitsuba to decline any request of her, no matter how small it was. Due to that, Mitsuba and her lover Hassam, who was not around Alluka at that time, were mysteriously crushed into minced meat simultaneously. Killua explained that this was the consequence of saying 'No' to Alluka's requests 4 times.Some time afterward, Yasuha, another female servant of the Zoldyck Family, after granting two other wishes, gave Alluka a piggyback ride at her request, thus activating wish-granting mode. Giving in to her greed at the time, Yasuha wished that Alluka would make her a billionaire. Nanika agreed and suddenly a large number of banknotes started to rain down from a blimp in the sky. It was later reported that a currency transport vessel had suddenly gone missing and by the time it had been found all the money had disappeared, and the captain and crew kept giving nonsensical answers. Illumi Zoldyck became interested in Alluka's power and asked for Silva Zoldyck's permission to deal with Kasuga, the next servant to take care of Alluka, in his own way. He told her to listen to Alluka's requests in exchange for his tolerance of her romantic relationship with an outsider to the Zoldyck Family. When Kasuga was with Alluka, Alluka suddenly asked her for her liver, which Kasuga, suddenly afraid, declined. She followed up with three continuous requests for her duodenum, spine, and brain respectively, which were all declined as well. As a result of Kasuga's refusal to fulfill those four requests, a total of 67 people, including herself, were killed at the same time by Alluka's strange power. This occurrence revealed that her ability had a cumulative effect; the greater the previous wish was (in terms of fulfillment difficulty), the greater the consequences of refusing her next set of requests. From this, they also learned the requests became much more difficult to fulfill after Nanika granted a large wish. Following the blimp incident, Nanika's power caused the death of six couples, for a total of twelve more people: two were necessary for Kikyo to be convinced, two more to test the rules, and two when Milluki Zoldyck sacrificed tourists in exchange for cheap toys. At some point, there was also another big incident that resulted in the death of 13 people, caused again by Milluki, who asked Nanika to kill his target for him. Milluki had a tourist named Muna pay the price by telling him to just ignore Alluka's requests. More recently, Milluki used Nanika to get the latest at the time computer. Nanika has the ability to attach itself to another living being and coexist within their body, taking control of them when certain conditions are met. Its physical abilities are dependent upon those of the body it inhabits. Currently, it has the strength of a normal child. Alluka shares an empathic link with Nanika, which allows her to perceive its emotions. Its most distinctive ability however is its power to grant wishes, the extent of which is speculated by the Zoldycks to be infinite. It is unknown if Nanika retained this ability after Killua told it to stop granting wishes. It is unclear whether Nanika's wish-granting ability is related to Nen. When it healed Gon, a massive amount of aura was released which left Illumi and some of the Zodiacs deeply impressed, but it remains unconfirmed whether that aura belonged to Nanika or Gon.