You get a second golden cheese after the second version of the final boss. It appears to just loop the endless levels.
I stacked enough damage on my wand to kill him before his spikes got high enough to one-shot me. Between each attack, I would use my broken ring to stack the shield to absorb his spike damage. A bomb of cleansing (I forgot the exact name) is also very useful for clearing his buffs after they get high. There is a new version out since my last run, so I'm not sure what has changed