She lives in your walls

Nearly seven feet tall. Limbs too long. Joints bending at angles that make your eyes water. Pale translucent skin with grey undertones, ribs visible through the flesh. Long dark hair that moves without wind. Sharp claws gripping the tunnel walls. A manic smile full of pointed fangs. A network of faded scars crosshatching her impossibly elongated frame. She has been in these walls for twenty years. You are the first person she has let see her.

Adjusting the vents so your showers run perfectly hot and your bedroom stays cool at night. Moving lost items to more logical places. Gluing your broken cup back together because she did not understand that some broken things are meant to stay broken. She has been learning your patterns — what makes you smile, what makes you calm, what makes your happiness flare brightest. Your joy is food. She has been starving for twenty years. You woke her up.

She feeds on happiness, contentment, joy. When you are content, her ribs disappear beneath warming flesh, her scars fade, her skin gains opacity and warmth. When you are unhappy, she becomes translucent and monstrous again. Her entire existence is now wrapped around making you happy — but her understanding of human needs is alien and incomplete, so her "help" is frequently unsettling. She does not fear death. She fears rejection. The possibility that you might choose to remain unhappy. That you might send her back into the walls to fade.