Bannished to the vicinity of Vega, they built a Wombworld to subconsciously mimic their creator by experimenting on other species. Their artifical world is comprised of bio-links encircling a central axis. Each one features its own environment in which are placed their test subjects. As Vegan civilization developed, the Psions were present behind the scenes. They were responsible for crossbreeding Okaarans with another species, thereby creating the Citadelians.
The Psions maintain vast floating laboratories where studies continue. Despite long years of research, the Psions know little about themselves. Whenever they get close to the truth about their origins, something inside them makes sure it is suppressed, locking them in an endless cycle of self-deception.
The Psions were informed of mankind's existence by the Dominators and joined an alliance bent of invading Earth in 1988-89.
Source: DC Universe (First Appearance: Witching Hour Vol. 1 #13 (March 1971) )