Alter Ego's consciousness was given to him by the Stranger and not naturally as originally theorized. A second world was also created known as Ego. Alter Ego was given to the Collector. The Stranger planned to one day set his two creations against each other to see who was the stronger. Alter Ego existed within the so-called "Black Galaxy," which is probably actually a dark nebula near or within the Milky Way Galaxy.
Alter-Ego vs. Ego
Ego flew too close to the Earth causing atmospheric disruptions, forcing Thor to investigate the disturbance. As Thor was about to stop Ego, he is interrupted by the Stranger who told Thor that he would not allow Ego's destiny to be interrupted. When Thor wants to know why not, the Stranger blasts him and tells Thor that Ego was his creation. Thor tried to deter him from reaching his final destination which was the Collector's Museum. Ego learned of his true origin and that he had a brother; Alter-Ego, who had been imprisoned by the Collector. Alter-Ego was created to despise his brother as the Stranger wanted to learn who was superior through battle. Ego reluctantly defended himself hurting his brother, but Thor stopped him before the final blow could be struck. The remains of Alter-Ego fell into Ego's orbit effectively becoming a moon, and together they travel the universe.
The Raiders' Attack
When the mercenary band known as the Ravagers struck a deal with Ego to let them set up a camp on his surface for a group of alien refugees, Alter Ego was targeted by the marauder group that was tormenting these aliens, Chargazel's Raiders. Before assaulting the refugee camp, the Raiders set up a device on Alter Ego's surface to modify its behavior. Since Ego's will was susceptible to Alter Ego, the moon's temper tantrum caused Ego to create environmental hazards to drive off all creatures on its surface. Ego managed to speak through the plants on his surface to the Ravagers and their allies, the Asgardians of the Galaxy, to tell them about the Raiders' meddling on Alter Ego. Angela flew up to Alter Ego and killed Chargazel, forcing the Raiders to disable the device and escape, thus returning Alter Ego to normalcy.