So... if you don't take the sticky paper with you into the hall with the moving crimson rings -- you're screwed?

If you reload, and grab the rings with the sticky paper then proceed to the next level... and then look up that you were supposed to use the little niche on the previous level to get 3 fire orbs... well... you're screwed again? There seems to be no way back -- I have 1 crimson ring on me but it isn't enough to get me through that hall again.

I must be missing something, right? There can't be so many game-breaking issues all clumped together near the end of the game -- can there?

You may have missed a tapestry in a previous section that drops a Crimson Ring when clicked on.

The start of the level (near the stairs you came from) spawns a Darkmoon Mage every time you use a Crimson Ring, and that Darkmoon Mage is guaranteed to drop a Crimson Ring, so as long as you can get there you can get "back" a Crimson Ring.

But yeah, the game screws you over with the Crimson Rings. This is why you Save Early, Save Often.

...and why you use different save slots.