PHOENIX IV
Jean Grey was replaced by the Phoenix Force entity in X-Men (1st series) #101, who then seemingly died as Dark Phoenix in #137. The real Jean returned in Avengers #263 and Fantastic Four #286, returning to life as Marvel Girl in X-Factor (1st series) #1. She abandoned any codename for a time in X-Men (2nd series) #1. Jean posed as "Redd Dayspring" in Adventures of Cyclops and Phoenix #1, and first assumed the mantle of Phoenix in #4.
Jean Grey has absorbed the memories of Madelyne Pryor and the Phoenix Force when it was posing as her during Inferno. Many of these memories still remain within her consciousness.
Jean began to manifest the power of the Phoenix Force, eventually becoming its full avatar before her death in New X-Men (1st series) #150. She returned to life in Phoenix Resurrection: The Return of Jean Grey #1-5, severing her ties to the Phoenix in the process.
Jean and the Phoenix reconnected during the Fall of X. After her death in X-Men: Hellfire Gala 2023 #1, Jean returned to the White Hot Room in Jean Grey (2nd series) #1-4. She resurrected through the power of the Phoenix Force and the sacrifice of Hope Summers igniting the first spark that gave birth to the Phoenix Force as an avatar of life and death, while also traveling through to ensure Hope was born as the "Mutant Messiah" to begin with. Effectively, this paradox of cause and effect means Jean Grey was responsible for the first manifestation of the Phoenix Force outside of time and space, retroactively making Jean and the Phoenix linked, now and forever.
Marvel Girl II is Valeria von Doom, III is Rachel Grey / Summers, Phoenix I is Baron Zemo.