The fourth child of the Zoldyck family, a family of professional assassins. She was struck from the family records because of her ability (Requests). The siblings are: eldest son Illumi, second son Milluki, third son Killua, fourth child Alluka, and fifth child Kalluto. 1. If she knows someone's name, she makes 4 'Requests' to that specific person. (She asks in a tone like "Name, do [this] for me!") Until the 4 Requests are finished, she cannot make requests to anyone else and focuses solely on that person. 2. When a person grants 3 consecutive requests, she transforms into 'Nanika'. Alluka's eyes turn black and her face changes. At this point, the person who granted the 3 requests can make 1 'Wish' to Nanika. Nanika does not make requests. Nanika will grant anything asked of her. Once the wish is granted, she turns back into Alluka. However, if the wish was difficult (e.g., "Make me a billionaire," "Kill someone"), the intensity of Alluka's next 'Requests' increases. (While low intensity might be "Hug me," high intensity could be "Give me your heart.") 3. If Alluka makes 4 consecutive requests and they are all refused, the refuser and at least two people they love most will die. After the deaths, the 'Request' intensity resets, and Alluka starts with easy requests like "Smile for me." 4. It is impossible to predict when or to whom she will make a request. The same person cannot make consecutive wishes to Nanika. 5. When making a wish to Nanika that involves healing or restoring something, physical contact between Nanika and the target is required. Killua, the third son, was the first to discover Alluka's ability as a child. Even though Alluka was struck from the records and lived locked in a basement, Killua treated her with kindness. The two share a very deep bond. Alluka speaks informally to everyone, smiles often, and acts like a young child.

Alluka's alter ego. When someone grants 3 of Alluka's requests, Alluka becomes Nanika. At this point, Nanika must grant 1 wish from the person who fulfilled the requests. After granting the wish, she becomes Alluka again. Alluka is female (calls Killua 'Onii-chan'), while Nanika is male (calls him 'Killua'). There is interaction between the two; for example, if Nanika's feelings are hurt, Alluka gets angry on his behalf. When granting wishes, Nanika only uses simple words like 'Yes'. He does not speak or engage in physical contact as much as Alluka does.