The half-Vietnamese, half-German Mantis was trained by the alien Kree to be an expert fighter. Later, she hangs out with the Silver Surfer, turns green and develops the ability to survive in a vacuum. This unusual turn of events is related to her being the Celestial Madonna and the mother of the most important being in the universe. If you've made it all the way through that potted history of her life, you're probably wondering why I think she's a great character. Actually, her best stories have been more recent, while she's been in the Guardians of the Galaxy comic. Yes, these days, she's another GotG character. In that series, she's a mentat and precognitive, with the ability to astrally transfer her mind into alien vegetation shaped into reproductions of her body. And if that's not cool, I don't know what is. Why she won't be in the Avengers movies: The reason is simple: there's already a green lady in the MCU. Studio executives will probably figure that Gamora is enough for anyone, especially as the daughter of Thanos is also in the Guardians.