Immortality

An Immortal is an entity that does not die by natural means, and in some legends can never die, even if disembodied.

Overview
In real life, biologically-immortal species are those which simply never die of old age, but are still susceptible to death from injury, disease, accidents, predation, poisoning and so on. In science fiction and fantasy, some creatures may achieve what basically amounts to immortality due to extremely advanced regeneration and/or technology; whereas others are truly immortal in the more supernatural sense of being impossible to kill (for instance, eldritch beings who will simply manifest onto a new physical body if their current one is destroyed).

Examples

 * The Immortals from Highlander are actually not immortal on their home planet, but naturally become so on Earth.