Already stated by its name, this rune has the power to change its wielders appearance. More precisely the dedicated element according to the current elemental day. This is more a curse than a blessing.
During the Fall of Kooluk the swordswoman Mitsuba is gifted with this special effect rune and that makes her hardly a reliable fellow in combat. You will notice soon the annoyance of having her equipment and items changed almost every battle to make them fit her present element. And you really can't think of any advantage given by this mixed blessing. Where this rune comes from and why Mitsuba attached it in the first place remains a mystery. - Celes