Myrna was originally a Ghil-Dirthalen who was given a physical form to act as a researcher for June. As an inventor, she aids his other servants in creating new, magical technology that makes Elvhenan what it is. Floating cities, bridges made of light, and more were because of their work.
She joins Fen'Harel's rebellion when the time comes, fearful of June when he joins the others in dabbling in the Blight and his cruelty. She specializes in destroying wards and screwing with the technology she worked so hard to create. Who better to take it down than one of the people who made it? She knew it best.