Secret room on the first floor? (Spoiler)

[Haios]

Right when you get the tempest (fury?) from the puzzle using the newly aquired magic map. If you go down the ladder and kill the two tiger striped worms, theres a wall with a notch (using the map) inside the wall. Its inside facing south, in the south east corner. If you try to knock on the wall there it wont make a sound like solid walls do, but i can't seem to open it or find any clue to how it is done. Anyone know whats in there and how to get it?

[Guest]

You need to walk backward into it.