Celestials

The Celestials were an ancient civilization who were present long before the dawn of the galactic communities and even the Dark Elves.

History
The origin and nature of the Celestials is shrouded in mystery. Whatever was known about them is known only to a few, such as Taneleer Tivan. Knowhere, an intergalactic port station, is actually the severed head of a deceased Celestial.

Characteristic Traits
The Celestials are gigantic beings, nearly the size of a small planet. While the most that has been seen of a Celestial is severed extremities, it is presumable that they are humanoid in shape.

Trivia

 * In the comics, the Celestials were deeply involved in humanity's early development, and were responsible for the creation of the Asgardians, the mutant X-gene, and the Eternals, the alien race that Thanos belongs to.