Did you equip the axe. Kamtoga gives it to you to break its armor...

I dont have the axe ive been hitting the minni boss for hourse

Alright listen up to beat the mini ice cave krawl you attack but the health willgo down
very little then kamtoga comes and gives you the cosmo axe then equip that as your weapon

As he says , kamtoga will give you a cosmo axe. Just go to the cosmo menu and go to
equipment. Choose weapons and the axe weapon. It will say new at axe.