Ozzel is a servant of Rezo. She first appeared in Slayers Revolution as maid to Gioconda, who was assumed to be the owner of Hellmaster's Jar then, since she specifically said that her orders were to "guard the jar and its owner" in EP09 (Slayers EVOLUTION-R). Despite being human in appearence, she is actually an artificial human doll.
Like Xellos, Ozzel remains polite towards people no matter what happens, even if they are enemies. While her body is incredibly lifelike, her head pops off at times in a comical matter, revealing her true nature.
* An alternate transliteration of Ozzel is Ozer, which is "Rezo" spelled backwards.