Mantis is a Celestial hybrid empath with the ability to sense other people's feelings and alter them. She was raised alone by her father Ego and later recruited as a member of the Guardians of the Galaxy led by her paternal half-brother, Peter Quill. Since she was a child, Mantis helped ease Ego's neurotic behavior with her powers until the Guardians came to his planet. 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. When the Guardians were called to action to stop Thanos from collecting the Infinity Stones, Mantis accompanied some of the Guardians to Knowhere where they failed to stop the warlord from gaining the Aether resulting in Gamora being captured. After, they traveled to Titan where they teamed up with Doctor Strange, Iron Man, and Spider-Man to fight Thanos head-on. The fight once again ended in failure, leading to Mantis and her fellow Guardians turning to dust. Fortunately, five years later, the remaining Avengers resurrected the victims of the Snap, bringing Mantis back to life. She then participated in the Battle of Earth. Afterward, she resumed being a part of the Guardians, with all of them reunited again, now joined by Thor. Months later, Mantis and the Guardians continued to operate alongside Thor, helping planets in need. However, when news reached them of the campaign of Gorr the God Butcher, the Guardians and Thor went their separate ways, setting out to aid those in need. The following year, with Christmas time nearing on Earth, Mantis traveled there in order to retrieve Kevin Bacon as a gift for the still grief-stricken Quill. Joined by Drax, the pair tracked down Bacon and successfully brought him to Quill, who immediately demanded they return him. Afterwards, Mantis finally revealed to Quill that they were siblings. Mantis is somewhat naïve, showing no offense when Drax the Destroyer refers to her as Ego's pet and not understanding what a practical joke is or that she embarrassed Peter Quill by revealing his attraction to Gamora. This is probably due to her being isolated with Ego for most of her life. Despite this, her use of higher-level vocabulary shows she bears intelligence. She holds a passive demeanor, always bowing her head in Ego's presence and being hesitant to attack anyone. This inevitably resulted in her having low self-confidence needing Drax to goad her on in using her powers against Ego. In spite of her loyalty to Ego, she was unable to condone him slaughtering his own children eventually telling the Guardians of Ego's true plan and working with them to thwart him. Even while fighting the cops when she and Drax attempted to bring Kevin Bacon to Knowhere, Mantis didn't want to kill them, but just put them to sleep. Even years later, her naïveté persisted as shown by her practicing a "mean face" after Quill sarcastically told the Guardians to do so as they neared the wreckage of the Statesman. Much like Drax, she was blunt to the point of open honesty telling Iron Man, a presumed enemy at the time, that Drax was unlikely to survive his Repulsor Cannons. Mantis was almost entirely non-malicious instead approaching Spider-Man out of curiosity. Despite her lack of weapons, she was a brave individual openly jumping at Thanos in spite of the Titan possessing four Infinity Stones and later using her powers to subdue him. Though maturing, her child-like mind-state still persisted as, in spite of Thanos' imminent arrival, she took advantage of Titan's fluctuating gravitational fields to mimic the effects of a trampoline. Mantis, while generally having a calm personality, is easily angered by Drax, possibly due to the fact that Drax was her closest friend. Since Drax was the one who encouraged her and supported her when she was still serving Ego, she acts most comfortably around Drax. After all the years with the Guardians, Mantis became more caring towards the other members, especially Peter Quill who was her half-brother. Initially, Mantis hesitated and didn’t want to tell Quill as she was afraid that will make them distant. Mantis is shown to be very considerate as she wanted to cheer Star-Lord up and hence decided to go to Earth during Christmastime in search for a Christmas present, even kidnapping Kevin Bacon to make Quill happy. She also expresses her consideration by preparing Christmas lights and decorations to decorate Knowhere for celebrating the holidays. Eventually, she told Star-Lord the fact that they were siblings and they developed a much closer relationship, with Mantis as Star-Lord’s actual family.