I am looking for a word that means unable to die AND unable to be killed? so immortal would not work in this case because an immortal person can be killed and invincible would not work because you can still die of natural causes. Is there a word that works for both?
According to https://www.dictionary.com:
not mortal; not liable or subject to death; undying
remembered or celebrated through all time:
not liable to perish or decay; imperishable; everlasting.