Hello @cryptofi,
I definitely would not look in that mirror :)
This is a nice creepy story that you develop well. I like the way you build mood and scene. You tie it up, by explaining you will never go in the attic. However, this would have been a good place to add some other creepy fact. Maybe someone else didn't know about the mirror, went in the attic and disappeared, or was never heard from again.
You did such a good job creating this scene that we are ready for more terror.
Keep writing!