Made by me His came from a professor. He wanted to create the ultimate killer machine, so he made Cero. The prof just teach him to fight. The only words he learned are his name and "kill". The prof made more test objects and let them fight against. The strongest are number 0-5. One day Cero ran away and killed everybody in his name. He met Thunder and he made him not brutal :3 (beat the hell out of Cero).