Headhunter Rabbit was a mercenary who hailed from a nation to the east of the Karsanas City-State Alliance, famous as a warrior and an assassin. Osk had signed a contract with him and hired him for a staggering amount. He had contracted with other workers or gladiators as bodyguards as well, but nobody else was paid as highly as him. At one point, Headhunter Rabbit foiled an assassination attempt on Osk. (Source: Overlord Wiki)