The character first appeared in Thor #132 (September 1966) and was created by writer Stan Lee and artist Jack Kirby.

Ego, the alien Kree, and The Colonizers immediately followed the creation of Galactus, thus establishing Marvel Comics' own "space age mythology".

[7]The first glimpse of Ego on the last page of Thor #132 is a full-page splash panel photo collage with his human features superimposed on a bulbous, chaotic planetoid.

[11] In gratitude, Ego takes in the Wanderers, a group of various alien races whose planets had been the first to be devoured by Galactus billions of years ago.

[12] The Rigellian Tana Nile took a sample of Ego to fertilize sterile worlds being considered for habitation.

[13] However, this drives Ego insane, and it soon gives in to its primordial urges and absorbs the Wanderers, which causes Thor to side with a returning Galactus.

[11] Ego then digests a number of Dire Wraiths to replenish its energy reserves, and battles the Space Knight Rom.

[23] When Quasar dies during the Annihilation war,[24] Ego was released back into the Universe, only to be approached by the Worldmind to join the new Nova Corps.

[27] Ego learns he was one of two entities created by the Stranger for a science experiment, and that his brother Alter-Ego has been held in captivity by the Collector since birth.

[29] Galactus, changed into the Life-Bringer by the Ultimates, encounters Ego after regaining his strength after a battle with the new universal construct Lagos.

Ego then reveals that before his creation by the Stranger, his consciousness was that of a man named Egros, similar to Galactus' former self Galan.

After formally meeting one another and putting aside their past animosities, Galactus uses his Life-Bringer abilities to form a body for the rest of Ego, who now calls himself Ego-Prime.

[33] However, the Guardians of the Galaxy discover that the cult is committing a mass sacrifice, encasing Ego in a dark shell.

Ego has various internal features similar to a biological lifeform, with his consciousness being contained in a giant, brain-like organ below the surface.

[11] Ego can also create clouds to block space attacks, raise his internal temperature, and manipulate his magnetic fields.

He can project energy blasts to obliterate starships or planets,[37] read minds and scan their biological structure,[38] and communicate to sentient beings using telepathy.

If his energy reserves diminish, Ego can restore them by devouring planets, tapping into stars, or digesting large numbers of living beings.

[35] Additionally, Ego is exceptionally intelligent, although as his name suggests, he harbors an extreme superiority complex and can be emotional if thwarted.

For a while, Ego was propelled through space via the engine Galactus implanted on his south pole, but eventually gained control of the ability to travel at faster-than-light speeds without it.

However, the Fantastic Four and Exiles convince Earth to oppose Ego, with Blink eventually killing him by drilling into his brain.

Additionally, he came into existence millions of years ago and learned to use his cosmic powers to manipulate matter and form an entire planet around himself as well as utilize many resources and a humanoid avatar to interact with other sentient beings.

American rock band Monster Magnet recorded a song titled "Ego the Living Planet" which was released on their album Dopes to Infinity.

[53] In the 2015 book Marvel Comics in the 1960s, Pierre Comtois stated that, "With the creation of Ego [Lee and Kirby], unbelievably, managed to equal if not top their introduction of Galactus only a few months before.