Mantis is a young empathic woman raised by the Celestial Ego and recruited as a member of the Guardians of the Galaxy. Since she was a child, Mantis helped ease Ego's neurotic behavior with her powers until the Guardians of the Galaxy came to his planet.
Real Name: Mantis
Portrayed by: Pom Klementieff
1. Guardians of the Galaxy Vol. 2
After bonding with Drax the Destroyer, she came to care for the Guardians and then allied with them to help prevent Ego from conquering the Galaxy. With her own servitude to Ego ended, she became a full-fledged member of the Guardians and accompanied them on further adventures. She has the ability to sense other people's feelings, and rarely alter them.
2. Avengers: Infinity War
When the Guardians were called to action to stop Thanos from collecting the Infinity Stones to wipe out half the universe, Mantis accompanied some of her group to Knowhere where they failed to stop the warlord from gaining the Aether.
After, they followed Thanos to Titan where they teamed up with the Avengers to fight him head-on. The fight once again ended in failure, and Mantis and her fellow Guardians, except Nebula and Rocket Raccoon, were killed when Thanos unleashed the stones' power.
3. Avengers: Endgame
Fortunately, five years after the Snap, the remaining Avengers successfully gathered the Infinity Stones from different points in the past, and Bruce Banner undid the effects of Thanos' snap, bringing Mantis back to life. She then participated and survived the Battle of Earth, attended Tony Stark's funeral after he sacrificed himself. Mantis then resumed being a part of the Guardians, with all of them reunited again, now joined by Thor.