Rachel Summers first appears in Days of Future Past, Uncanny X-Men #141–142. The future she comes from has mutant detention camps, dead X-Men and Sentinels controlling people's…

Rachel Summers first appears in Days of Future Past, Uncanny X-Men #141–142. The future she comes from has mutant detention camps, dead X-Men and Sentinels controlling people's lives. Scott Summers and Jean Grey are her parents in that future. Rachel helps send the adult Kate Pryde's mind back into her younger body to stop Senator Kelly's assassination. It's Kate making the trip, with Rachel providing the psychic help that makes it possible. So Rachel is part of that story before she ever becomes a regular member of the present-day X-Men. She's already lost people, already lived under the Sentinels and already reached the point of trying to change history because there are so few options left. That gives her a very different starting point from a new student discovering powers. By the time the team gets to know her, she's bringing the memory of what can happen to all of them. To her, those deaths have already happened.