It’s a little hard to find the cellar at first; there’s a door that leads to what was probably once a kitchen, but has been violently smashed to bits. One wall is covered in half-finished bricks, empty wine bottles scattered about the floor. There are words painted in bloody red ink on the wall, dripping in places as though it were just recently painted. The words read:

“Lo, a shadow of horror is risen
In Eternity! Unknown, unprolific!
Self-clos'd, all-repelling: what Demon
Hath form'd this abominable void
This soul-shudd'ring vacuum?—Some said
“It is Urizen”, But unknown, abstracted
Brooding secret, the dark power hid.”

In the middle of the checkered tile floor is a trapdoor. There doesn’t appear to be any lock on it, or a knocker. There is only the imprint of a hand, one with sharp pointed nails.

You can go back into the living room from here.