Zepar has the appearance of an imp, with a potbelly, horns sprouting out of his head and bat wings on his back. He appears to always have a mischievous smile on his face.
Zepar initially presents himself as a vainglorious individual who does not like it when things does not go his way. However, he was not nescient about this fact, as he aplogised later for his initial behavoir, as Zepar was dissembling his true motives so he can test his King Candidates. Zepar believes that a king must live a lonesome existence, being au fait of the fact that the betrayal, of a king's allies, would cause the quietus of a king and everything he ruled; thus, like Leraje, Zepar prefers if the world was not ruled by a single king.
A member of Zepar's Household is Pisti.
In this form, Sinbad has the appearance of a small imp with dragon wings, hooves, two pairs of horns, a furry tail, and a third eye. His voice also becomes childlike.
In this form, he is able to perform an incredibly loud scream, via Sound Magic, that is able to "command" others into doing something. When used on Kougyoku Ren, he told her mind to sleep. Sinbad has stated that because it is a tasteless move, it affects everyone in the vicinity to some degree. Not only can he do that, but he can also control other people's minds by using a special type of sound wave. He does this by forcing his own rukh into their body. Sinbad had done this with Kougyoku during their fight and to two other unknown people, one of whom Sinbad stated lives in his territory. He says he does this so that he can know everything in the world. This was the reason that he could come out with countermeasures against the Kou empire so quickly.
- His name is probably taken from the book The Lesser Key of Solomon. In the first section of this book, entitled Ars Goetia, several demons are described, Zepar being the sixteenth. As a matter of fact, the dungeon where Zepar resided was the 16th as well.