In The ShowEdit
Gwen Tennyson is the cousin of the famous Benjamin Tennyson, who traveled with him and her grandpa Max in the first series. In the series Ben 10: Alien Force, she later fought the Highbreed, and once again Vilgax. She also created a more personal relationship with Kevin. Then, in Ultimate Alien, she fought Agragore, and once again fought Kevin as a mutation due to his atempts to absorb the Omnitrix/Ultimatrix. Gwen is partially an alien race called the Anodite, made of pure energy with ability to cast spells, although she is also part human (Infact, more so), so it is difficult for her to mantain a form of pure energy. This suit is that form, in which she loses most of her humain features (Like fear), and gains great powers mostly underminded by the power of the suit.
Note: Although she appears in the first one Gwen does not appear in this form in Ben 10.