>>58912848Xerneas's powers, as well as one of the two functions of Ultimate Weapon, are to grant eternal life.
However, in Z-A, they decided to add that this wasn't possible for humans.
It's worth noting that immortal doesn't mean invincible. It means that an immortal being can be killed by disease, another living being, a natural disaster, or an accident. Immortal beings simply have the characteristic of not dying of old age; it's like keeping their cells perpetually young.
>>58912857Volo is not immortal. He appears to belong to a race/people with a lifespan far exceeding that of other humans.
He can therefore age and die like any other living being; we simply don't know the average lifespan of this people.
