I just attempted to do fight kiln, got to final boss and decided to use constitution and invulnerability crystals, but neither of them worked, in fact when I used got hit more when I used them than before I used them, especially invulnerability. When I clicked invulnerability it seemed to take away a chunk of my HP. I was going for my melee cape so I'd have all 3 capes. I never has issues with the crystals the other 2 times I did fight kiln.
MB: Gigabyte GA-990FX-Gaming, CPU: AMD 9590 8 Core, GPU: Sapphire Nit*o R9 390 8gb, RAM: G.Skill Sniper 1866mhz 16gb, SSD: Samsung 860 EVO 500gb main drive, SSD: Kingston HyperX Savage 480gb, HDD: WD blue 1tb