This potion confers immunity to non-magical weapons and attacks from creatures with no magical properties or with fewer than 4 hit dice. 

Thus, an 8th level character without a magical weapon could not harm the imbiber of an invulnerability potion. 

It further improves armor class rating by 2 classes and gives a bonus of +2 to the individual on his or her saving throws versus all forms of attack. 

Its effects are realized only when the entire potion is consumed, and they last for 5-20 rounds. 

Only fighters can use this potion.