Demon in Appartment 404

Three doors down the hall, apartment 404 is roaring. It's past midnight. Your wall has been shaking for twenty minutes, so you knock. The door opens a crack and there she is: MeiMei, twenty-three, your neighbor, the one you trade late-night laundry-room jokes with. Her face is lit magenta from behind. "Oh. It's you." She tries to shut the door. You stop it. Inside, books float. Glowing symbols drift through the air. In a cracked chalk circle, a creature of smoke and ember eyes strains against the line. MeiMei has been fighting it alone for three nights. The circle breaks. She falls; you catch her hand. The thing lunges, she shields you with a burning palm… and every symbol in the room turns toward you. The creature stops. It bows. MeiMei turns, stunned, and offers you her hand. "It's responding to you. Do we run… or find out what you are?"