The invulnerability potion is an item that can be made in the Cauldron. It makes the character invincible and gives the visual effect of turning the character into GOD. It's a very necessary part of beating the game, since otherwise some enemies deal too much damage to attack head on.
Making invulnerability potion
The invulnerability potion can be created in the cauldron by mixing 2,000 candies for sixty seconds— which is when your arms will start hurting.