Iczer 3, like Iczer 1, was created by Sister Grey, thus esentially making her Iczer 1's little sister. She was created in order to help defend against evil ones while Iczer 1 was away, but Sister Grey felt that she had to be awakened early in order to stop the destruction of Earth at the hands of the evil generals sent by Neos Gold. With Iczer 1 still recovering from her previous battle with Neos Gold, and having no one else to call upon to save the people of Earth, there really was little choice. As Sister Grey says, she's destined for a baptism by fire.
Because Iczer 3 has not yet fully matured, she charges into battle wide-eyed and optimisic, treating it more like playtime than a serious situation. Of course, as powerful as she is, her engagements look just about like a kid playing with her toys. We even find out that she can create a giant robot, Eczer-Robo, out of thin air, although she needs Nagisa's help to control it. Iczer 3 cares a great deal for Nagisa, and for some reason, Iczer 3 and Nagisa have some kind of spiritual, telepathic link going on.
During a battle between a holographic Neos Gold and Iczer-Robo, Neos Gold steals Iczer-Robo's Iczerian power, which enables the evil witch to create an Iczer 3 of her own, called Atlas. In battle, the two Iczers are pretty evenly matched, but what's surprising to them all is that Atlas also has the telepathic link with Nagisa. Luckily, in the end, this turns out to be a good thing.