The planet known as Klatuu orbits a star that emits in the X-ray frequency. The planet was originally inhabited by a race known as the Kr'll who had dealings with the Shi'ar and were given psychic dampeners by them for some unspecified purpose.
Sometime well after the early 26th century, the Kr'll were warned of the coming of Galactus by The Keeper. To save themselves, the Kr'll built a fleet of starships and fled their world but the machines they left behind continued to function without them. However, for some reason, Galactus did not consume the planet.
A long time after the Kr'll exodus, the Vision arrived on Klatuu while searching for the mutants who had left Earth just before the War of the Worlds. The Vision interfaced with the central terminal on Klatuu and became one with it, eventually relinquishing his humanoid physical form and renaming himself Main Frame.
At some point, someone brought Captain America's Shield to Klatuu and left it in Mainframe's custody. Clues in the Book of Antag were designed to lead those who sought the shield to the planet where they could be tested by Main Frame to determine if they were worthy enough to carry the shield.
In 3017 A.D., the Guardians of the Galaxy and the mercenary team known as Force both arrived on Klatuu. After participating in seven one-on-one contests, the Guardians barely won. Main Frame awarded the shield to Major Astro and teleported the defeated criminals far away.
- Kr'll race (formerly)
- The idea that Klatuu orbited a star that gave no light because it only emitted its energy in the X-ray frequency is scientifically unsound. All stars radiate the energy that they produce across the entire electromagnetic spectrum and that ALWAYS includes a lot of visible light. Only black dwarfs would not emit light and the universe isn't old enough for any of them to have formed yet.
- In Guardians of the Galaxy #5, the Omniscient Narrative states that, if either the star or the planet that orbited it had a name, it had been long since lost to antiquity. However, the Silver Surfer knew the name and it was often mentioned in later adventures.