Eternals are individuals that have been given unfathomable power by their Eternity Swords. The relationship between Eternal and Eternity Sword is one of companionship, as the Eternity Swords are powerful enough to have full-fledged personalities of their own. In some cases, they can force their will upon their wielder to gain an advantage in battle. When someone becomes an Eternal, they must be completely severed from the time axis. That is, all evidence and effects the Eternal had is nonexistent the moment they become an Eternal. Because of this, they stop aging from the moment they became an Eternal, and become immortal by practically all means. Usually, the only one who can defeat an Eternal is another Eternal.
All Eternals fall under two categories: Law Eternals and Chaos Eternals. Law Eternals follow their Eternity Sword's will and seek to reform all things back into a great singularity. Chaos Eternals fight against the Law Eternals and for the lives and worlds the Law Eternals wish to absorb or destroy.