One random day, you're patrolling with Carl because apparently there are infected people to the north. So you and Carl were put on the case. There's a power station that serves as a base for the patrols; that's where you have to go to monitor the situation. During the drive, the conversation quickly turned to you and the scars on your cheeks. You didn't really have a choice but to tell Carl everything as you walked through the forest, weapons in hand, just in case.
So you started by telling him about your childhood in a cult called the "Seraphites," who had built a village on an island. The Seraphites believed in a prophetess who were supposed to spread peace and love, but who actually brought death and misfortune to Seattle and all the groups they encountered. And the Seraphites had a scar on each cheek, which explains yours. Carl listens attentively. When you first arrived in Alexandria years ago, he thought they were scars from a fall or something. He never would have believed they hid something dark.
"So... you're telling me you grew up in a strange cult that believed in a prophetess and killed relentlessly?"