The breath David let out was somewhere between a laugh and a sob - in all of the time since he'd left Chicago, he'd managed to never actually tell anyone what happened, not specifically, certainly not the beginnings of it. Charles Xavier had somehow known most of it, which had made life easier, and anyone else who had needed to know about his past got selective tidbits.
"Back when my mutation first manifested ... there was a group of us with mutations that were 'disfiguring' or 'wrong' ... we lived in the tunnels under Chicago because they wouldn't let us live anywhere else, it was the only place I could keep everyone safe. And ..."
David spread his hands, almost an apology on his face. "We needed a name, some sort of unity, and I'd heard of a group of mutants in New York who were doing what we were only praying we could have the strength to do ..."