Illumi is often completely expressionless. Illumi has long, jet-black hair with a bit of uncombed hair behind his head. He also has large, dark, pupil-less, black eyes. Illumi disguises himself as Gittarackur by using large, round headpins to reconstruct his facial structure and musculature.
Illumi’s hair was shorter when he was younger. Illumi wore long sleeves and a shirt under his shirt, as well as gray pants.
Illumi speaks “cheerfully” Illumi displays little expression for most of his life. Illumi speaks with a joyful, absent-minded tone that contrasts his expressionless demeanor. Illumi is a hardened, ruthless individual who focuses only on his own interests. He still has a strong and protective love for Killua, his younger brother. In fact, he used his Nen power to control Killua to ensure Killua’s survival and obedience.  His father taught Killua that darkness was his only source of support and that he only found joy in the death of others. Illumi inserted a needle into Killua’s brain to protect his brother. This forced Killua to flee from the battles he didn’t know he could win.
Illumi takes care of most Zoldyck Family members. Open to handling Alluka’s power even if it means his death. However, he has said that family members cannot kill during inner missions (a mission in which there is internal conflict). He implied that Alluka would be okay with his killing and that Alluka was not part of his family.
Illumi Wanders off the path of an Assassin
Although Illumi appears to be devoid of human emotions, he still has a strong desire for Alluka’s wish-granting ability. Tsubone suggests that evil ambition to control Alluka’s power led him to take a different path than an assassin.
Illumi and Hisoka once had a “give-and take” relationship
Developed a strange relationship with Hisoka at one point. He described it as “give-and take”. once volunteered to help the magician, serving as his double in the Phantom Troupe hideout as Hisoka searched for Chrollo. Hisoka then asked whether he would kill Killua. Showed a horrible side and asked if Hisoka was willing to die right away. Hisoka’s demeanor, bloodlust, and reaction to not making a decision on whether to kill Gon or not were similar to Hisoka’s response to the Hunter Exam. However, his relationship with Killua is less important than their relationship. Believed that one would end up killing the other, despite the mutual benefits of their relationship. Agreed to sign a contract with Hisoka, stating that if the magician was killed, would receive his reward. It was referred to as an “engagement ring” or “prenuptial agreement”, by the assassin.
Background Teenage Illumi
Illumi, the oldest child of Silva and Kikyo, was trained from birth in assassination. His father and trained Killua to be an elite assassin.
He learned Nen at some time during his childhood. Silva’s younger brother, inserted a Nen needle in Killua’s brain to control his actions and development. The needle caused Killua to flee from battles that he was not certain he could win. He also formed a partnership with Hisoka sometime before the 287th Hunter Examination. This partnership was not explored.
Illumi was sent to the Hunter Exam by his mother after Killua ran from Zoldyck’s manor Plot
Hunter Exam arc Illumi Disguised as Gittarackur
Briefly appears in the Hunter Exam’s first sections, but his appearance is severely distorted by the countless pins. Tonpa offers him his laxative-laced liquid, and he first appears. assists Hisoka when he is unable to find his way to the second stage due to Menchi’s temperament. He is one of the three examinees who passes the third phase.