Alluka is revealed only much later in Hunter x Hunter, despite being part of the Zoldyck family, simply because the entity within her, Nanika, is currently "uncontrollable." Her own father dismisses her as "emotionless," but Killua clearly sees that his sister wants nothing more than someone to care for her.

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An old photograph of the Zoldycks shows Kikyo with Illumi, Milluki, Killua, and Kalluto pleasantly facing the camera, but Alluka is clearly located away from the rest of them. Not that it matters what her family thinks about her, anyway, because Killua is the only one whose attention she seeks.

10 Is Alluka A Boy? No, But It's Complicated

Hunter x Hunter — Little Alluka

Alluka is called "brother" by Milluki, Illumi, and even Morel (a Hunter sent to exterminate the Chimera Ants). This is contradicted by Killua, who always refers to her as a girl — in one case, he claims that Alluka's gender is why the Zoldycks hired female butlers, like Tsubone and Amane.

Most important, however, is the fact that Alluka uses feminine terminology to introduce herself, which is all the confirmation anyone needs.

9 Is She The Youngest Zoldyck? No, That Would Be Kalluto

Hunter x Hunter — Zoldyck Family photo

Alluka is 11 years old to Killua's 12, and their two older brothers, Illumi and Milluki, are 17 and 24 respectively. Kalluto, the initially shy boy who bears his fangs when he joins the Phantom Troupe as their new #4, is age 10, making him a year younger than Alluka and the youngest of all five Zoldyck children.

Interestingly, despite her youth, Alluka is technically more powerful than her entire family put together, but the complexity of her powers makes them quite difficult to use in combat.

8 What Is Nanika? An Entity From The Dark Continent

Nanika hxh

Nanika is an as yet undescribed being that allegedly arrives from the Dark Continent, which is the considerably larger landmass beyond the known world in Hunter x Hunter.

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Nanika's true nature is a mystery, but its capacity to "grant wishes" — after passing a number of stringent requirements — makes it quite a useful tool for the Zoldycks. It's a good thing that nobody except Killua completely understands how Nanika works, then.

7 Who Is The First To Observe Nanika? Killua

Hunter x Hunter — Nanika and Killua

Killua is the first person who notices that his sister is "possessed" by something that turns Alluka's face into a Japanese horror movie ghost. He thankfully keeps it a secret, knowing that his parents and siblings would only use this knowledge to ostracize Alluka.

Unfortunately, when a butler named Mitsuba discovers Nanika manifesting in the little girl and tells Silva and Kikyo about the situation, Killua has no choice but to come clean (to a point).

6 What Special Privileges Does Killua Get? He Can Order Nanika To Do Anything He Wants

Hunter x Hunter — Alluka hugs Killua

There are so many rules and regulations to Nanika's abilities that it seems impossible to effectively obtain a wish that one wants. For instance, denying Alluka's petitions four times consecutively will always result in the death of the person involved, not to mention that wish-seekers cannot transfer Alluka's requests to anyone else.

Killua, however, has the unique advantage of being able to "command" Nanika to do what he wants, even if it means bypassing those before him.

5 How Many People Have Died Due To The Zoldycks' Experiments On Alluka? At Least 80

Hunter x Hunter — Alluka Experiments

Kikyo Zoldyck begins the first series of experiments on her daughter with Mitsuba, which concludes in the latter's rather painful death. The next step is carried out by Illumi, who orders another butler, Kasuga, to interact with Alluka, who proceeds to ask the servant for her body organs.

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Unable to grant the little Zoldyck girl's requests, Kasuga perishes, taking sixty-seven others with her. In addition, Nanika's wish-granting has killed around 10 to 15 more people.

4 Can Alluka Use Nen? Not Currently, But Nanika's Powers Are Enough

Alluka protects Killua in Hunter x Hunter.

Being a Zoldyck, it's highly likely that Alluka has a massive reserve of Nen like everyone else in her family. The presence of Nanika, though, means that the host child has never had any need to exhibit her own powers.

Interestingly, it is still not confirmed if Nanika's wish-granting is based on Nen — but given the sheer number of bylaws included, it sounds like a Specialist ability (like Kurapika's Emperor Time, except vastly more impactful).

3 Why Does Milluki Use Nanika's Powers? To Assassinate His Target & Get A New Computer

Hunter x Hunter's Milluki Zoldyck talking on the phone.

Illumi describes Alluka's powers in a flashback, one section of which revolves around his younger brother, Milluki. It seems that the latter went for a stroll with Kalluto and Alluka, interacting with a photographer (whom he plans to assassinate).

Milluki manipulates the man in such a way that he rejects Alluka's petitions, leading to him being killed. He has also made his sister commit murder as a simple test, but the most despicable thing Milluki has ever done is use Nanika to get himself a brand-new computer.

2 Is There A Limit To Nanika's Wish-Granting? Apparently Not

Hunter x Hunter — Killua hugs Nanika

It's true that Nanika demands a whole host of prerequisites be satisfied before giving people what they desire, such as being aware of the asker's names and preventing a person from continuously asking for wishes.

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That being said, every single wish is granted (sometimes literally), and the Zoldyck family believes that there is no end to the number (or scope) of wishes that can be requested. Then again, Killua orders Nanika to never use its powers again, so the whole point is moot.

1 When Is Alluka Last Seen In The Story? Before Gon's Ascent Of The World Tree

Hunter x Hunter — Gon, Killua, Alluka

After Nanika restores Gon, it has a teary farewell with Killua when the latter claims that he only wants to protect his sister and the entity within. Much later in the story, Killua reveals to Gon that Alluka had saved him (through Nanika), which makes Gon thank all three of them profusely.

They all go their own way when Gon reaches the World Tree, where his father, Ging, had said he would be waiting for his son to have a real conversation. Alluka is presumably touring the world with Killua at the moment.

NEXT: Hunter X Hunter: 10 Best Battles In The Anime, Ranked