Mortals = normal.
Lesser Immortals cannot die from old age.
Immortals cannot die from age or disease
Greater immortals cannot die from age, disease, or poison
True immortals are just that: immortal. Like the highest of gods.
However in my campaign lesser gods would be greater immortals with massive powers, so they could be overthrown, but it kinda takes followers and such. Ascension is such a cool goal. And the least of gods are weak enough they could still participate in the occasional adventure.
I tend to seperate it into mortals, ancients (haven't died yet), immortals (can still be stabbed) and eternals (have always been and will always be, as old as the universe and unkillable).
If I made this template I would slow down limb regeneration to day based and I would take away the strenght and dex bonus but increase the con bonus. But I didnt' make this template so my opinion is not important.
"that nighted, penguin-fringed abyss" - At The Mountains of Madness, H.P. Lovecraft
When a man decides another's future behind his back, it is a conspiracy. When a god does it, it's destiny.