Project: P.E.G.A.S.U.S. (Potential Energy Group / Alternate Sources -- United States) was a hidden government research facility in the Adirondack Mountains, experimenting with various forms of energy production. Because they also studied the energy production abilities of certain super-criminals, Pegasus also doubled as a prison at times as well.
Project: Pegasus has employed various super-heroes as security chiefs and staff, including Quasar, Blue Shield, Darkhawk, Guardsman, Firebolt, Thing, Giant-Man, and the Squadron Supreme while they were stranded on Earth-616. Test subjects have included Wundarr, Klaw, Solarr, Electro, Moonstone, Blackout, Rhino, Vector, X-Ray, Bres, Nitro, Nuklo, and others.