Marvel has secretly rewritten what it means to be tied to the X-Men's Phoenix Force. A cosmic force of death and rebirth that predates this universe itself, the Phoenix Force has been subject to constant retcons since it was first introduced. Recent comics have had a particularly dramatic effect, however, completely rewriting the lore - sometimes in quite surprising ways.
The Phoenix Force has chosen a new host in Jason Aaron's Avengers run, the vigilante Echo, and in so doing it has revealed it is also the Thunderbird of Native American mythology. "The blood of the Cheyenne flows through my veins," Echo thought as she was granted the power of the Phoenix o. "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." But another unnoticed retcon has taken this one step further, redefining what it means to be bound to the Phoenix Force.
Beings who wield the power of the Phoenix are traditionally known as Phoenix hosts, for they are human beings who possess its power. But Kieron Gillen and Kei Zama's Eternals: Celestia one-shot includes a flashback to an encounter between the Eternal Ajak and one of the first Phoenix hosts, Firehair, 100,000 years ago. Surprisingly, Ajak considers Firehair not a host of the Phoenix - but an avatar.
It may seem like a subtle change, but it's an important one, because it helps define the relationship between the Phoenix Force and those it chooses. These Phoenix avatars are not just expected to wield the power of the Phoenix; at some level they also commune with the cosmic entity, and as a result they are called to act on the Phoenix's behalf. No doubt some avatars commune more closely with the Phoenix than others, explaining the apparent "apotheosis" of Jean in Grant Morrison's New X-Men run, in which it became difficult to tell where Jean ended and the Phoenix began.
It's interesting to note this particular retcon was carried out in an Eternals comic ahead of a major crossover, "Judgment Day," that will bring the X-Men, the Avengers and the Eternals together in one spectacular event. The Avengers include the current Phoenix avatar, Echo, while the X-Men's ranks are bursting with former avatars. It's quite possible the timing of this retcon is no coincidence, with future X-Men comics exploring the Phoenix in a whole new way. If that is indeed the case, then this retcon could have a major effect on X-Men lore - especially for Jean Grey.