I've explored almost all of Level 5, except for several rooms on the right.

I haven't found any way into the rooms on the right except for the bottom corner.

I found this one room in the column next to the far right where an arrow of yellow tiles points to a 'shutter' type locked door going right. The Lens of Truth reveals no clues, and none of my weapons or items appear to open the door. There's no enemies either.

Does this door open somehow? Or is there a completely other way to the right?