The planet Eyung (also known as Eternus), in the Andromeda Galaxy, was home to a race called the Eternals, a warrior race who held domination over countless planets long before the time of Earth.
Eyung was destroyed by the Gigantians of the planet Gigantus in retaliation for attacks on their home world. The entire Eternal race was wiped out except for Grom their greatest warrior. Grom was implanted with the minds of all his people before being shot into space in suspended animation.
In modern times Grom, now known as the Over-Mind, had made failed attempts to carry out his people's last wish of universal destruction.
Originally unnamed, the planet was named "Eternus" in Over-Mind's entry in Official Handbook of the Marvel Universe #8, when the Eternals were renamed "Eternians", and later "Eyung" in Quasar #15 and #16 (where it was also named "Eyungia"). In Official Handbook of the Marvel Universe Master Edition #9, the planet was named Eyung, with "Eternus" between brackets.