Sadaso

Sadaso (サダソ, Sadaso) is one of the three fighters that challenge Gon and Killua on the 200th floor of the Heavens Arena. Having reached the 200th floor without the use of Nen, he was "initiated" after being attacked with a malicious aura attack and lost his left arm.

Personality
Sadaso is mean and ambitious, willing to do everything in order to become a Floor Master.

Heavens Arena arc
Sadaso is one of the three fighters that challenge Gon and Killua on the 200th floor of the Heavens Arena that target rookies for easy wins to become floor masters.

Sadaso kidnaps Zushi with his nen hand to make Gon comply with his demands, namely having Gon forfeit in a match. However, Killua learns of the fight between the two and makes a threat against Sadaso's life, frightening him enough to leave Heaven Arena for good. Its unknown if Sadaso wears a mask, which is commented by a ticket seller when hes talking to Killua. When he leaves Heaven's Arena after Killua's threat, he is wearing sunglasses/goggles for the first time and his face looks less pale than before. At this point, when he is leaving Heavens Arena, he calls Gido to warn them that Killua will come after them next.

Nen
Sadaso is a Transmuter, so he specialized on giving a specific form to his aura.

Trivia

 * In Nippon Animation's adaptation, Sadaso has both arms intact. His physical left arm is always seen protruding from his tunic, leaving his left sleeve dangling. It is unknown if he can move his real left arm.