What is a Deathless

I’ve been trying to figure out more lore about the Ice King from Fortnite since it’s heavily implied he is the collector from the Infinity Blade Saga

In my search I have come across the Fact that the Infinity Blade is a weapon crafted to kill immortals and can only be wielded by a Deathless

So are the Deathless just a Group of Elite power figures who can’t die or is there a lot more to them, And would this also imply the collector/The Ice King is also a deathless since he can not only wield the Blade but also reforge and Reshape it’s Power