Mordred thinks back. She found you at a guild safehouse, which must have taken some doing, since you'd only just dropped in for a bite and to fence some cheap jewelry. She said she had to make a long trip down south, and asked if she could stay in the safehouse for a few days while she got ready, and if you could help get her out of the city unseen. You already knew the Iron Sphere was missing and there were rumors that Edvers Kells was involved, but she didn't mention any of that, so you didn't ask. You called in a favor, found her a closet to sleep in, and left to go about your daily business and give her some space. But soon the word on the street was that Edvers had been arrested, and when you stopped by later that evening, she said she was ready to leave. Now.
On your way through the sewers, you couldn't help but asking her what was going on, if there was anything else you could do to help. She was uncharacteristically quiet, didn't say much. If you had to read the look on her face, it told of dread and determination, not acute fear. "Dad's innocent," she said a few times, but it felt more like an affirmation for herself than an attempt to convey information to you. You knew better than to ask anything about where she was going.
When you made it to a sewer outlet outside the city walls, she hugged you and said: "Turn back now, Mordred. You can't go with me any further. I don't know when I'll be back, but I'll see you repaid for helping me today, I promise." She hesitated a moment, as if debating something in her head, then picked up a rock and scratched something onto the stone wall: a crescent with six points extending from the convex side. "That symbol? If you ever see it, you're in danger. If you see anyone wearing it...avoid them. At all costs."
Then she squeezed your shoulder, took a deep breath, said goodbye, and started walking away, never looking back.