zabuza became known as the devil when, at about the age of twelve, he killed more than a hundred genin's at the final graduation exam of the hidden mist village. hidden mist village was also known as the blood mist village. they discontinued the exam after this incident.

years after, zabuza became a missing nin and after failed coup attempts, he let himself be a shinobi for hire to raise money for his revenge. he worked for gatou who commisioned him to assasinate tazuna, the bridge engineer for wave country.

determined to prove that he wasn't called the devil of the hidden mist for nothing, he set out to kill tazuna. in his first fight with kakashi, he nearly defeated the famous copy ninja by trapping him in a water prison. without naruto and sasuke's help, kakashi would have remained trap in the bubble until zabuza decides to despatched him. on their second fight, he had prepared himself against the sharingan, having seen what it was really about. it was merely a technique that requires attention to detail, body copying, jutsu copying and hypnotism.

he called off this fight when gatou and his men showed up, ready to kill the shinobis so that he doens't have to pay him. this apparently had been gatou's scam all along. gatou then mocked zabuza. saying he's not the devil zabuza, he was merely... a cute little baby devil. zabuza admitting to naruto that he had lost, borrowed naruto's kunai. catchin it with his mouth as his two arms were now useless....he rushed towards gatou who in turn commanded his men to kill them. the men raved, one against this many...hah! as zabuza rushed towards them, they could see his chakra rising over him, a dark, dangerous ki, in the shape of what he is known. zabuza went thru them slashing left and right, cutting a path thru gatou's men. his eyes that of a beast. his body a pincushion of swords. yet he ran till he reached gatou. they continued to stab him. die already, they cried. you and i together can go to hell, he said to gatou. even the unremarkable devil of the hidden mist can become a real devil in hell. and with a sway of his head, sliced gatou's head off, proving once and for all that he was indeed, the devil of the hidden mist.