Billions of years ago, on the planet Maltus, the Maltusian immortals studied all aspects of life. They took local reptiles for testing and discovered one part of the lizard's mind had the potential for much greater complexity. They enhanced the creatures and found the new developments were passed to each succeeding generation. The reptiles were released back into the wild to chart their survival rate.
The Maltusians eventually left their world in a great exodus. The enhanced life forms evolved into the Psion race. The early Psions investigated the Maltusian labs and mimicked their creators. They went as far as cutting off their tails to look more like the Maltusians (and as a result, disavowing their original background). After several millennia, the Psions left Maltus to follow their creators, now known as the Guardians of the Universe, who were on Oa.
When the two discovered each other, things were not quite what the Psions expected. The Oans regretted their decision not to destroy their equipment before leaving Maltus. The Psions were forbidden to travel to Oa, though they wished to learn more from the Guardians. Though the Psions had mastered the technology, they had gained little understanding. The Guardians felt responsible for the Psions and sent them to the Vega system, where they could strive for comprehension. The Guardians ordered the Psions to stay within their assigned area so the Guardians would not be disturbed, as the system was off limits to the Guardians and the Green Lantern Corps for other reasons. The Guardians hoped the Psions would achieve their own greatness in time. The Guardians' great hope has not yet come to fruition.
Discovering their creators and then feeling humiliated, the Psions buried the truth about themselves. As a species, they forgot their background and began anew their scientific work. But as scientists, the Psions asked the questions all thinkers ask: "Where are we from?" The Psions never stopped asking this question. Again and again, the Psions discovered the truth about their origins, and every time they ended up suppressing the knowledge. The Psions refuse to acknowledge to themselves that their creators did not want them nor believe in them. When hearing the truth, in pain, they go into shock and incapacitate themselves. This process also suppresses their knowledge of their genesis.
The Psions maintain vast floating laboratories where studies continue. There they exploit the lifeforms they found in the Vegan star system. Working with their science, they created the many species of Vega's twenty-five worlds, subconsciously replicating their own origins. Active against them are the Omega Men, an interstellar group of rebels drawn from the Vegan worlds. In their research, the Psions gave X'Hal virtually supreme power, which she ultimately used against them. The Green Lantern Corps is still barred from entering or interfering within Psion designated space; however the Corps and its masters, the Guardians, are now considering removing that restriction.
One of the Psion experiments involved attempting to synthesize the bio-replication powers of the Czarnians. They maintained a laboratory on an unidentified asteroid in the Vega star system. Years after the experiments had been abandoned, the Omega Men came to the asteroid and inadvertently activated the Psion experiment, duplicating the Omega Man known as Tigorr. 
The Psions also attempted to see how much energy a Tamaranean body could hold, experimenting on Princess Koriand'r of Tamaran and Princess Komand'r of Tamaran. The two escaped the Psions' clutches, but not before absorbing so much solar energy that they gained the ability to shoot energy from their hands, known as Starbolts.
A small contingent of Psions were captured and enslaved by an alien race known as the H'San Natall. It was the H'San Natall's intention to seed the planet Earth with various sleeper agents whose bodies would be genetically modified to harness great power and fight against Earth's Metahuman populace. The H'San Natall enslaved a number of Psions and put them to work bringing their plans to fruition from a laboratory on the moon of Titan. For sixteen years, the Psions monitored the progress of eight genetically altered humans, one of whom, Audrey Spears, was raised in a virtual reality chamber on Titan. Audrey, and three other of her fellow seeds, escaped Titan with the help of the (now teenage) hero known as the Atom. Kidnapping a Psion scientist named Dorek, they returned to the world of their birth and became the second group of young heroes to call themselves the Teen Titans.
In later years, Green Lanterns Kyle Rayner and Guy Gardner planned to breach Vegan space in order to retrieve recruit Soranik Natu. The mission was successful, though the Guardians expected the Psions to react to the incursion into their territory. More recently, the Guardians repealed the ban on the Vega system, allowing the Green Lanterns to operate with the system. The Guardians anticipated that the Psions would react with hostility to this.
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