WARNING: The following contains spoilers for Phoenix Song: Echo #1, available now from Marvel.
The Avenger known as Echo began as an ally of Daredevil and is now one of the next heroes set to appear in the Marvel Cinematic Universe. A gifted warrior in her own right, Echo is poised to make her onscreen debut in Hawkeye before transitioning into a lead role for her own Disney+ series.
In the comics, she's even gotten a far more powerful boost thanks to her current role as the new host of the Phoenix Force. Despite being usually affiliated with the X-Men, the Phoenix saw something truly impressive in Echo -- even if she doesn't quite understand it herself. Phoenix Song: Echo #1 (by Rebecca Roanhorse, Luca Maresca, and Carlos Lopez) hints at the true reasons the cosmic entity chose her, and how she's being set up to confront an ancient Marvel evil.
During the "Enter the Phoenix" storyline, the cosmic force returned to Earth in search of a new host. The Force chose a number of candidates from across the Marvel Universe and pitted them against one another, with the apparent prize for victory being an infusion of cosmic power. The Avengers and their fellow heroes did their best to keep the Phoenix Force out of the hands of more threatening candidates like Namor and the Red Widow, and conflict brewed between the champions over who could be trusted with the nearly immeasurable level of power that was up for grabs. One of the chosen heroes was Maya Lopez, aka Echo. Born deaf and trained in the art of combat, Echo has been recognized as one of the Marvel Universe's most skilled heroes.
In the Phoenix Tournament, Echo faced Namor and despite a brief power boost from the Phoenix Force was overwhelmed when the battle was relocated to an underwater setting. A far more favorable place of battle for the Sub-Mariner, Echo ended up losing the fight and was left for dead at the bottom of the ocean. However, while Namor and the other combatants kept fighting, Echo refused to give up. The Phoenix Force was impressed by how Echo adapted to the threat and refused to stand down even when facing a cosmically-empowered Namor, and elected to choose her as its new host. However, this has not been an easy transition for Echo and she is dealing with doubt over the Phoenix's decision.
Echo eventually decides to consult an old mentor named Chief and comes across his protege, Riverwalker, who explains that his power is to travel through a person's family line and view their history. When Echo notes that she still can't understand why she was chosen by the Phoenix, Riverwalker notes that not only did she refuse to die even in the most dangerous of circumstances, but that she also descends from a long-line of warrior women. The Phoenix Force must have believed that only Echo was truly prepared to contend with an upcoming threat that is teased to be the powerful mystic entity known as the Adversary.
It turns out that through her ancestral line of strong women, the Phoenix Force sees the opportunity to contend with the threat better than almost any of the other candidates it had chosen. It gives Echo a deeper connection to her mother's history in the process, allowing her to fully embrace the legacy that her family has left for her as a warrior. Considering the Phoenix's history of bonding with strong women (which extends to the dawn of humanity), the entity's choice speaks to the potential within Echo to become an ideal champion and host.