Con was built by Unity, with the help of Mr. Fixer and The Argent Adept, using bits of Omnitron. But that doesn't properly tell the story of Con, or who Con IS.
Hey! I gave a (mostly) straight answer! I deserve a cookie.
From the Reddit AMA
Enjoy
All of that is as I expected... except for the Adept. Huh. I wonder what he had to add?
Musak for the elevators.
Brilliant!
Well, I suppose it doesn't call itself the Concordant Harmonic Entity for nothing.