How did you beat the 18 level boss? Also does the endless mobs after that get even more health and attack than the first endless? Currently on level 14, just taking a rest before cuz I been playing too much.
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