In reality, the human body of Ego is just a host body for the Celestial entity who is in essence a floating brain in space. He was born centuries ago, and after becoming aware of its own existence, was able to control the molecules and matter around itself, eventually building a planet as an extension of itself. It wanted to know more about the cosmos and the other life that occupied it, so he created an avatar of different lifeforms to blend into each alien culture. But he was very dissatisfied with what he found, so he took it upon himself to reshape those worlds to his own will, having planted seeds into each planet. But he needed two Celestials to complete his goal, so he impregnated females across the galaxy, hoping that one of them could summon the power necessary, but all of them were unsuccessful, so he killed each of them.
However, there was one success in the form of Peter Quill (Star-Lord), who comes from Earth. Ego wanted him from childhood, but his collector, Yondu Udonta, betrayed him, realising that all the other children he had been killed by Ego, and took him into his Ravagers clan. Ego eventually found Star-Lord after hearing about how he saved Xandar from being destroyed by Ronan using the Orb. All Star-Lord wanted was to find his father, after his mother had died from cancer, but after learning that it was Ego who heartlessly orchestrated it to achieve his own selfish ends, Star-Lord turned against, and with the help of the Guardians of the Galaxy, killed Ego at his core.
- Guardians of the Galaxy (2014)