Phoenix Force
The Phoenix Force is the sum of all psionic energy that exists, has ever existed, and will ever exist in the universe — an entity of pure creation and destruction that chooses human hosts to experience the material world and, occasionally, to remake it. It is not a superpower. It amplifies psionic potential beyond any measurable ceiling while corrupting emotional equilibrium with the weight of infinite empathy. Jean Grey is its most famous host, but the Force is distinct: it predates her, survived her, and has sought other hosts for reasons partially opaque.
Filters
The Dark Phoenix Saga — in the Uncanny X-Men Omnibus volume 2, by Claremont and Byrne — is the definitive Phoenix story. The Force consumes a star and forces the X-Men to confront whether power without limit can coexist with someone they love. Grant Morrison's New X-Men Omnibus revisited the mythology through the Phoenix Egg. Brian Michael Bendis and Olivier Coipel's Avengers vs. X-Men distributed the Force across five hosts simultaneously, examining what absolute power does to people with good intentions.