This article contains spoilers for Avengers #44
The full Dark Phoenix when they wield its power.
The Phoenix has returned to Earth, seeking a new host, and it has taken a strange approach in order to gain it. This cosmic being has pitted numerous Marvel heroes and villains against one another in a strange tournament, although it's not been particularly clear what it is looking for in a host. Indeed, Doctor Doom was the only one who realized the Phoenix had its own inscrutable agenda, forfeiting his match against Captain America when he deduced the Phoenix was not looking for his particular character traits. The action has continued to escalate, with the rounds becoming increasingly brutal, and in Avengers #44 the Phoenix Force finally made its choice.
The new host of the Phoenix Force is the street-level superhero Echo, a Native American who has traditionally been depicted as a ing character in Daredevil comics. The timing is convenient to say the least, because Echo is soon to make her MCU debut, played by Alaqua Cox; not only will she appear in the Hawkeye Disney+ TV series, there have been reports she'll have her own spinoff as well. It's clear Marvel Comics has decided to increase Echo's profile significantly ahead of her live-action introduction.
Marvel has taken this opportunity to expand the mythology of the Phoenix Force as well, revealing the Phoenix Force is also the Thunderbird of Native American mythology. "The blood of the Cheyenne flows through my veins," Echo thinks as she is granted the power of the Phoenix. "Like many of the native tribes, my people have always believed in a winged spirit of change. A great bird of fire that brings the summer. That protects us from the things that would feed on us, in the darkness and the sea. In the long, cold winter. Today, for better or worse, I have become that change." It is reasonable to assume Echo's perspective on the Phoenix is precisely why it has chosen her as its latest host, for it has come to Earth because a new winter is coming, with Mephisto rallying his forces to plunge the Earth into darkness. As interesting as this idea may be, it's a little anticlimactic in the context of the overarching narrative, because Echo was eliminated from the contest at an early stage, brutally beaten by Namor the Sub-Mariner - so violently that all the other competitors heard her screams through their own temporary Phoenix-bonds.
Avengers #44 ends with Jean Grey reaching out telepathically to offer her advice to Echo, a smart way of signifying the X-Men's own connection to the Phoenix Force has come to an end in the age of Krakoa, and that Jason Aaron believes his story will make Echo as important a host as Jean Grey herself. Given Jean's own iconic relationship with the Phoenix, it will be fascinating to see if he can pull it off as Echo's Avengers story continues.
