The cathedral is "separated" in 2 sections, that are interconnected near the teleporter going up then right. You have the "upper" part that leads to the boss with a bomb + 2 walls, that has to be started from the 1st layer (you have to unlock this by going back to the initial area where you get petrified, can be done by unlock the door on the top-left when you enter the labyrinth).How do you unlock this door? I can't find the boss of the Oz sanctuary
Then you have the "lower" part that starts from the teleporter in the sanctuary, then going up > left (by entering from the 3rd layer), that leads to the central part of the chappel with the dying knight in your screenshot.
In both cases, you'll need to place the statues to open the doors (either in the 3rd or 1st layer).
