“Phoenix” follows Jean and Sara two years before the latter’s death, shortly after she developed her Phoenix abilities. But for Marvel’s EIC at the time, Jim Shooter, Phoenix had gone too far. When X-Factor #1 hit stands in 1985, it would feature all of the surviving OG X-Men, plus a resurrected Jean Grey. So Claremont offered a compromise: instead of bringing back Jean, what about having Sara’s mutant powers manifest? Sara never had a triggering traumatic event, unlike Jean, who watched her childhood friend die in front of her.