History
Ego was a living planet and a long-time enemy of Galactus. When his presence threatened all life on Earth, the Fantastic Four and Thor both fought Ego, but he proved too powerful for them. So they requested the assistance of Galactus. Galactus agreed and combined his and Thor's powers to hold off Ego. While Ego was distracted, Thing launched an attack on Ego's brain, destroying it and putting an end to Ego.[1]