Illumi Zoldyck

Illumi Zoldyck (イルミ＝ゾルディック Irumi Zorudikku) is Killua's eldest brother. He is an experienced assassin, whom along with his father was responsible for Killua's training and upbringing. During the 287th Hunter's Exam, Illumi disguised and concealed his appearance, using special pins to change his entire facial structure to the point where he can only be recognized by his voice. An oppressive aura from him makes even Killua fearful and wary whenever he approaches Illumi.

Illumi holds a twisted and emotionless love for Killua. Illumi and Silva raised Killua to believe that the only thing sustaining him was darkness, and that the only joy he received through the world was in causing the death of others. He was also responsible for planting a needle within Killua's brain, forcing the latter to run from battles he wasn't sure he could win. Illumi did this to ensure that Killua would able to live to carry on the family business and as a means of protecting his little brother. This needle is self-extracted by Killua in the battle against Rammot.

A certain amount of friendship is shared between Hisoka and Illumi, although it is unclear as to how it could have developed. Illumi once came to the aid of Hisoka by standing for him as a double in the Troupe hideout whilst Hisoka attempted to find Chrollo.

Nen Ability
 * Although never explicitly stated, Illumi may use his nen in order to assist him in his disguises. Near the end of the Yorknew City arc, he poses as Hisoka as a favor to him, but can only keep his transformation intact for five hours or so without using pins to hold the shape. Besides that ability, he was shown controlling the recently deceased body of one of the Ten Dons during the Phantom Troupe arc. He has also used his pins to force an assistant helping the Hunter Test examiners to truthfully answer his question, however, it is unclear whether the pins forced him to only tell the truth or whether it was due to the pain and disfiguration the pins caused.