Path of the Immortal

Barbarians that follow this path are generally more level-headed than others, and channel their rage into becoming a an unstoppable force of nature. They are nigh impossible to kill as long as their rage persists.

Iron will

While raging, you become a more formidable version of yourself, and all damage you take is reduced by your constitution modifier (minimum of 0), to a minimum damage of 0.

Vitality

Your enhanced vitality brings multiple benefits even when you are not raging. For every 5 years you live, you only age 1 year. Additionally, you become immune to the poisoned condition.

Unstoppable Rage

Your rage makes you nearly unstoppable. While raging you can no longer be charmed, frightened, restrained, or stunned. If you rage while any of these effects are on you, they end immediately. Additionally while raging, you maximum speed cannot be reduced except by effects that specify specifically your speed becomes zero. 

Vital Surge

Your rage grants you near unstoppable vitality. When you rage, you gain temporary hitpoints equal to your barbarian level. Additionally, when you would fall to zero hitpoints while your rage is active, your rage ends, but you fall to 1 hitpoint instead, and gain temporary hitpoints equal to double your barbarian level.