Potion of Invulnerability

Potions of invulnerability are only usable by warriors and bestows great defensive effects upon the drinker for a short amount of time. It's sold at the Sorcerous Sundries, but the first one is gained from Silke if she killed during her subquest.

In-game description
"This potion confers very high resistance to all attacks, while giving bonuses to all saving throws. The effects of the exilir last for 5 turns but can only be used by warriors."