This character only appears in the first El-Hazard TV Series - Wanderers.
Crayna Crayna is a legendary Holy Priestess of Fire. She was the priestess who was predecessor to Shayla Shayla and served with Miz Mishtal and the Priestess of Wind who came before Afura Mann.
Little is known about her, but what we do know we see through Shayla's memories. When Shayla was a young child, she had a chance encounter with this great priestess in the forest. Shayla was amazed as she watched the priestess practice her craft. The priestess noticed she had an audience and smiled at the young girl. It was then that Shayla resolved to be just like that mysterious woman and thus entered the seminary (in her own rather unique way.)
As Shayla studied, once again the pair's paths crossed as Crayna was touring the school and recognized Shayla as that young girl, now all grown up. It can be argued that the second meeting gave Shayla the inspiration to study even harder and to move onto the next stage of her training.
After that, we know nothing else about her except that she and the priestess of wind both retired and Afura and Shayla became their replacements, chosen because of their command of the powers and knowledge of the elemental schools.
Physically, she looks like an older, more mature version of Shayla with bright red hair and a penchant for miniskirts and gems.
No reason is given for her retirement, but one can consider many options. Maybe she found love and married and thus retired (Much as Miz did in the OVA timeline.) Perhaps, it is just a general practice that chief priestesses retire relatively young (Before they reach middle-age.) A reason to explain this thinking is that a chief priestess obviously has more responsibilities and thus must use their powers more. That is probably a terrible drain on their bodies and when they show signs that they can no longer perform at their peak, they step aside and allow the next generation to assume the duties of protecting El-Hazard & keeping holy dogma. Perhaps then, the former chief priestesses retire to quiet obscurity, or more likely, they end up teaching at the seminary, passing their wisdom to future generations of holy servants.