Diane is the fourth and last sister the Mystic Warriors™ encounter in the first season. Her beauty hides her unimaginable hatred towards humans. Unlike her other sisters, she has absolutely no mercy for humans and her strength is far greater than the others. She was a phoenix, like her other sisters, but after the transport, she began to train with a mysterious character and became very powerful in both body and mind. Her battle techniques are unmatched and uses them with all her might. She has kept a dark secret for 500 years so deep she never revealed it to anyone. Her techniques usually involve sword techniques, but she also has the ability to morph her sword into other weapons such as a large boomerang or a fire crossbow. She visits the place where her sister and the other phoenixes once lived peacefully. Enraged in how the place was abused and maltreated she destroys the whole city in the area. As she watched the city burn to cinders, Spiralis contacts her and tells her she needs aid. Diane goes to Brownsville at once and battles the Mystic Warriors. The Mystic Warriors barely escape alive. Diane was about to destroy the city but Spiralis tells her there's too many innoscent people living in town. Diane agrees, but she still wants to destroy the Mystic Warriors. Diane passes as a regular human for a time and meets Angel, Crystal's best friend. Angel is the only person Diane likes on earth and rather gets close to her. Diane shows compassion only to Angel.