She once was a human, but made a pact with a powerful Demon. She sold her soul to this entity to become strong enough to protect her village. She fought off the enemy troops but was exiled by her own people some time afterwards as she slowly transformed into a Demon. It took one year before her whole body was covered in scales. Her demon pact giver ceased to exist before he claimed her soul entirely and she inherited some of his powers turning her into a Morpher and dragging her to Hell.
 
Her time as a demon made her lose some of her empathy. She has accepted and learned to like her demon nature, but part of her wishes back her human life. From an outside perspective she seems pretty cool and sometimes she’s not that talkative. There are ancient tales of her slashing through lines of enemies covering the soil in blood. These are known by historians and summoners alike. As she turned into a demon, many summoners tried to use her and her powers for their purposes.