Ego

"I call it the "Expansion". It is my purpose, and now it is yours as well. Over thousands of years I implanted thousands of extensions of myself on thousands of worlds. I need to fulfill life's one true purpose, to grow and spread, covering all that exists until everything is... me!"

- Ego to Star-Lord Ego was a Celstial being and the biological father of Emma and Peter Quill (aka Star-Lord and Star-Queen and the Quill siblings.

Biography
From Ego's page on the MCU wiki:

Apparition in the Galaxy
Over millions of years ago, Ego's origin remained unknown by nature although Ego remembered himself being born unaccompanied, parentless and bodiless; he came into existence as a being belonging to an ancient primordial race known as the Celestials. Despite dwelling in extreme loneliness for years, he discovered the ability to manipulate molecules and matter, which led him to construct a protective core around himself. Over the course of many years, he continued to build planetary layers over the core which evolved into a planet itself. The interstellar coordinates of Ego's planet were G52 22C848T12F+E16UC22.

Afterwards, Ego wondered about the purpose of his existence. To search for purpose and meaning, Ego created a biological humanoid avatar, which was an extension of his consciousness, to explore the cosmos and dwell among galactic civilizations to learn and experience about all galactic civilizations he encountered.

Dividing and Conquering
During his exploration into the cosmos, he found his discoveries "disappointing" when it came to dwelling among civilizations in all thousands of planets he explored. Upon realization, Ego conjured up seedlings and implanted them on thousands of planets before the seedlings were capable of terraforming all visited worlds into new extensions of himself.

Ego called this plan the 'Expansion'. He only had one problem; the seedlings could only be activated with the combination of two Celestials' powers. Therefore, he impregnated thousands of female alien species then hired Yondu Udonta to deliver the children; on the other hand, the children all failed to inherit the Celestial gene so Ego killed them painlessly and hid their skeletal remains in the depths of his self-constructed planet. . In the late 1970s, Ego visited Earth to plant his seedling in the wooded areas of Missouri, United States. Later, he met human Meredith Quill and awed her almost instantly, under his disguise as a "spaceman". During their romantic relationship, in 1980, Ego and Meredith conceived their first and second child named Peter Quill and Emma Quill, who would successfully inherit Ego's Celestial DNA, becoming his first children to grant the power of the Celestials.

Ego realized that he was genuinely infatuated with Meredith and that his feelings for her could put him off-task to settle with her instead of forwarding his plans to conquer the cosmos. Because of this distraction, Ego deliberately (yet reluctantly) implanted a brain tumor on her, leading to her death in 1988, before leaving Earth. In the hospital before death, Meredith described Ego to her children as beings composed of pure light.

Over the weeks leading to Meredith's death, Ego instructed Udonta to deliver his children to him. Udonta, however, now realized that Ego has been recently killing all of his prior children he delivered to him. Horrified and guilt-ridden, Yondu decided not to deliver Peter or Emma. Instead, he became the adoptive father of Emma and Peter Quill and raised them to be a Ravager. He probably told the Quills this to keep them from going off to find their father.

Ego later adopted an orphaned girl named Mantis and raised her as his own.

Physical appearance
To be added

Personality
To be added

Powers and abilities
To be added.

Family

 * Peter Quill/Star-Lord - Son and Attempted Victim
 * Emma Quill/Star-Queen - Daughter and Attempted Victim
 * Thousands of Unnamed Offspring † - Children and Victims

Allies

 * Merh Quill † - Former Lover and Victim
 * Thousands of Unnamed Former Lovers

Enemies

 * Guardians of the Galaxy - Attempted Victims
 * Gamora
 * Drax the Destroyer
 * Rocket Raccoon - Killer
 * Groot - Killer
 * Mantis - Former Assistant
 * Yondu Udonta - Former Employee
 * Keira Udonta
 * Captain Victoria
 * Nebula - Attempted Victim
 * Kraglin Obfonteri - Former Employee and Attempted Victim
 * Sovereign
 * Ayesha