Mantis

In the comics, besides being a highly skilled martial artist, Mantis has telepathic abilities that enable her to sense what others (opponents or not) are feeling. The Guardians of the Galaxy: Vol. 2 trailer reveals that these abilities have been translated into the movie, as well, as demonstrated in the final scene of the trailer, in which she reveals what Star-Lord feels for Gamora.

So she, like Drax, is a very sincere character – although, I hope, they have different reasons for being so. Could that scene be the one in which Mantis is introduced? It may be – after all, the characters wouldn’t have this conversation later on in the movie, as if she weren’t aware of Star-Lord’s identity…

Regarding their location, they may be on Knowhere, which now serves as headquarters for the Guardians of the Galaxy. And, given her abilities, Mantis might try to act like a psychologist, trying to counsel the other heroes, while also proving her worthiness.

Also – she looks awesome!