Asked in DC Comics
If the Guardians of the Universe are immortal then why are they able to die?
It seems as if most writers have approached the species as a
long-lived one; near immortals rather than true immortals. The fact
that they have grey hair seems to support that they do
However, even immortals often can still be killed, take the case of vampire meets stake, Highlander meets sword to the head, etc. It usually just means that they are able to live without aging and survive forever if they are able to avoid accidents, injuries, and any other specific vulnerabilities.
The Gaurfians of the Universe are immortal, but not immortal.