Mantis was every bit as important in the formation of the 2008 Guardians of the Galaxy as Peter Quill. Suffice to say, she was a highly influential member of the team. As both and empath and a telepath, Mantis' skill set is a fit for any team she's on, including the Avengers of which she was also a member at one point. In the current monthly Guardians series written by Brian Michael Bendis, Mantis is not on the team. She did make a cameo appearance, though, which is exactly what she could do in the film. There has always been a bit of romantic tension between Mantis and Quill so perhaps they could run into each other at some point in the film in which a hint at a previous relationship could be dropped. If Guardians of the Galaxy is successful enough to earn a sequel, count on Mantis as one of the favorites to join the team if Marvel decides to expand it like they are with the Avengers.
