Notorious for his cruel and deceitful fighting ability, Hisoka has proven to be deadly. His deviousness and volatility has made many opponents have difficulty anticipating his next move, and this has led to him winning many battles. Using Shu powered poker cards as his primary weapon, he throws them with ease and deadly accuracy.
Also, he is very intrigued by Gon and the potential this young boy has to become an adept and powerful adversary. Hisoka, ever looking for a strong opponent, is willing to aid, or at least not defeat prematurely, someone that could develop into a future opponent.
Sometime into the series, Hisoka is revealed to be a recently joined member of the Genei Ryodan, though his association with the organization is, rather characteristically, simply in order to fight a remarkable opponent. In actuality, his membership is a farce, a fact he later reveals at an opportune time.