Thousands of years ago a coalition of alien races joined together to create the Lifestone Tree in the hopes of creating a group of super beings to protect their interests. The Lifestone Tree was comprised of artifacts left over from the Big Bang that various species had collected and brought together. The species known to be involved included the Kree, the Skrull, the Shi'ar, and the Badoon, but presumably at least 4 other races participated. The eight beings who were empowered were nicknamed the Guardians of the Galaxy but this would seem to be a bit of a misnomer as the Badoon occupy the Milky Way Galaxy, the Kree occupy the Magellanic Clouds, the Skrulls occupy the Andromeda Galaxy, and the Shi'ar occupy another unnamed galaxy.
It is known that four of the Chosen Eight died in battle, two others died of old age, one retired, and the fate of the eighth is unknown. With the Chosen Eight inactive, the intergalactic peace between the alien species fell apart. The Lifestones were evacuated from Kree-Lar to prevent them from being stolen by space pirates, but the ship carrying them was shot down. Due to a fissure in space, many fragments of the Lifestone Tree fell to Earth and empowered a number of beings including the Sphinx; Moonstone; Basilisk; Blue Diamond; Ulysses Bloodstone; Man-Wolf, and Dr. Spectrum.
The Thunderbolt known as Moonstone would seek out the origins of the Lifestone Tree after she began to receive memories from Ajes'ha, the Kree member of the Chosen Eight. Ajes'ha was the original wielder of the Moonstone and the memories of previous owners appear to be recorded by the moonstone. I.S.A.A.C. eventually helped Karla Sofen purge herself of Ajes'ha's influence. It was later implied that Karla Sofen's predecessor Lloyd Bloch and his Counter-Earth counterpart were driven insane by their Moonstones, although not necessarily due to Ajes'ha's influence.
The Lifestone Tree concept may be connected to Darkhawk, the Fraternity of Raptors, and the Tree of Shadows. During a battle with another version of himself, the Sphinx summoned Moonstone, Basilisk, Ulysses Bloodstone, Starwolf, and Gyre, a member of the Fraternity of Raptors. With the exception of Gyre, the Sphinx and the ones he summoned were all known to be powered by fragments from the Lifestone Tree.
It was originally claimed that the Lifestone Tree was created as a collaboration between several alien species for the benefit of the galaxy. This is seemingly inconsistent with the creation of the Fraternity of Raptors, which were said to be created to ensure the supremacy of the Shi'ar empire.