Zelgadiss Greywers was once a human.  He became greedy for power in his early-teen years, however.  One day, while he was training, Rezo showed up and offered Zelgadiss the power he wanted if he would find the Philosopher's Stone Rezo was searching for.  Zelgadiss agreed, but he didn't consider the consequences.  Rezo turned Zelgadiss into a chimera, one-third human, one-third demon, and one-third golem.  When Zelgadiss complained about this in the first episode seen with him and Rezo interacting, Rezo stated that Zelgadiss had wanted more power, and he did get it, the chimera form was simply the most convenient way of giving him the power he sought.  So in that sense, it's Zelgadiss' fault for the way he currently is, but it's also Rezo's fault for not specifying how Zelgadiss was to receive his new power.

       Zelgadiss is pretty anti-social.  Usually when he's out in public, he wears a mask and hood.  This is to keep people from seeing his chimera form and freaking out.  He doesn't let anything get in the way of what he wants, or anyone.  He harms Lina in one episode to obtain an orihalcon statue, and in NEXT uses her to get a manuscript of the Claire Bible (which is burned in his hands, the unfortunate little chimera-man ^_^ ).  Even through this, he is a loyal friend and a determined fighter, though rather serious at times.  He's obsessed with finding a cure for what he calls his "freakish state."  He doesn't like Xelloss very much because he finds him incredibly annoying.  Not to mention Xelloss burned a copy of the Claire Bible before Zelgadiss got a chance to read it and see if it had a cure for being a Chimera.   Let's just say Xelloss didn't make a very good first impression.   Zelgadiss gets along well with everyone else.

       Zelgadiss' specialty is Shamanism, specifically, Spirit Shamanism.   Spirt Shamanism is magic which draws it's power from the astral plane.  Unlike Lina, he doesn't overkill his most powerful magic spell, the Ra Tilt (if you don't know which spell Lina overkills, then you don't watch Slayers that much, do you?).  He's one of two people in the series who is capable of casting the Ra Tilt spell, the other being Amelia.  He's also good with a sword, and uses a spell called Astral Vine to enhance it in some fights. He has an added advantage in sword fights because of his stone skin.  No sword can harm him except for the Sword of Light.