Project: Pegasus is a research facility in the Marvel Universe, initially seeking alternative energy sources and eventually becoming a prison for supervillains.
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Project: Pegasus is seen in Iron Man Armored Adventures, led by Russian scientist Anton Harchov. In this version, Project: Pegasus is an energy research facility located in New York City and is responsible for the creation of the Crimson Dynamo armor using Ivan Vanko as a pilot. It later becomes absorbed into Stark International under Obadiah Stane, who uses his head of security, O'Brien, to helm the new Dynamo armor.
P.E.G.A.S.U.S. appears in the Marvel Cinematic Universe. In Captain Marvel, it is a joint venture between the United States Air Force and NASA housed at an Air Force base. Later, "Phase 1", better known as Project: P.E.G.A.S.U.S., was a joint venture between S.H.I.E.L.D. and NASA, formed to investigate phenomena beyond the range of conventional scientific understanding. Both major contributors provided scientific expertise to the project, and due to the highly sensitive nature of the research conducted there, S.H.I.E.L.D. also provided its security force. It is also where Dr. Wendy Lawson experimented on a new drive for transportation for the refugee Skrulls. Project: P.E.G.A.S.U.S. played host to the Tesseract for many years, its scientists completely baffled by the object. By the early 21st Century, they had determined that it was an incredible source of energy, but they had found no way to tap it. This changed when S.H.I.E.L.D. Director Nick Fury found Culver University Professor Erik Selvig, and brought him in to investigate the object. Upon seeing it, he readily agreed to probe deeper, although unbeknownst to everyone at the time he was also being influenced by Loki.
Eventually, Selvig came to a rudimentary understanding of the Tesseract's capabilities, although he was taken quite by surprise when it began to exhibit a curious energy build-up. Project: P.E.G.A.S.U.S. was hastily evacuated, but not before Loki himself appeared, apparently having triggered the Tesseract remotely to open a portal for him to reach Earth. In the confusion, Loki made his escape (along with Selvig and Agent Clint Barton as mind-controlled allies), but the unrestrained energies released from his transit finally erupted to consume the entirety of the Project: P.E.G.A.S.U.S. facility, leaving a vast crater in its wake of destruction. The final death toll measured in the dozens.