The door in-front of Belladonna was designed in such a way that it was unassuming. It was simply stone, carved in a standard rectangle, with a slight indentation in the door to act as a handle. It looked like a first attempt at a secret door in a mansion, one that you designed for the fun of a 'secret door' but didn't actually make it too secret for fear of losing where it was. There were no special designs or secret messages inlaid into the design.
It was just a door, carved into the wall. Its location and the inhabitants were what made it stand out the most, as well as the multitude of scratch marks that covered the stone.
These scratches populated around the handle, along the edges of the 'doorframe' and at the floor in front of the door. It looked as if the Grimshawls had been trying to get inside of the door, eventually resorting to trying to dig their way through, but they only left a few scratches.
