Wallace "Wally" Sage was a powerful psychic. His psychic powers gave life to one of his comic creations, Flex Mentallo. Wally had Flex go on adventures with several other mis-fit heroes in a comic called 'My Greenest Adventure'. It was written all in green.
Later, Wally was captured by the government to work with the Men from N.O.W.H.E.R.E in the Ant Farm. During this interval, Flex had become powerless. Wally restored his powers, allowing Flex to free Wally. Finally free, Wally died.
Flex Mentallo mini series
In the Flex Mentallo mini series, Wallace Sage is represented as a veteran rock star in the middle of a suicidal crisis. In an hallucinogenous trip he talks to somebody (really, the reader) talking about the comics he grow about. He discovers than he has become the worst enemy of Flex mentallo but also he is the one who can save the multiverse from his own cynism.
Powers and Abilities
Wally was able to create things with his mind. He (unwillingly) created weapons for the Men from N.O.W.H.E.R.E, and also created Flex Mentallo.
In Other Media
Wallace Sage appears in season 3 of Doom Patrol. His first and only appearance of the season is in episode 7, "Bird Patrol." He is called Wally, and he comes to the Bureau of Normalcy in the 1940's looking for work.