Another venue, the energy research facility Project Pegasus, was also briefly used, though the unsuitability of such an institution for use as a general prison led to the imprisonment of most criminals there being discontinued eventually. The US Government then set about building a unique penitentiary dedicated and designed exclusively for the detainment of super-human criminals. Using expertise, research and technology pioneered at Project Pegasus spearheaded by Dr. Henri Sorel, and extremely robust materials such as adamantium and osmium steel, they built an underground three-level structure over below ground level in the Rocky Mountain range in Colorado. Prison security guards wore armoured Guardsmen uniforms, similar to the original Guardsman's armor, used technology adapted from Iron Man's designs. As a part of the "Armor Wars" storyline, Iron Man originally disagreed with this unauthorised use of designs and this led to Iron Man to forcibly remove all technology, resulting in jailbreak though the escapees were quickly recaptured. Iron Man's opinion later partially changed and went on to contribute to a later Guardsmen design, limited to work only in the Vault itself and the close environs thereof. The Vault's first individuals to be detainedwere 11 members of the Avengers' East and West Coast branches who were suspected of treason. Though they eventually escaped, it was only with outside aid as they found the facility internally impenetrable. They were eventually cleared of all charges. After those events, the prison filled with inmates, as super-human criminals were transferred there from all over the country. It quickly became the site of numerous breakouts and break out attempts. One of the most frequent escapees was the villain Venom escaping from the institution at least twice, killing many people in the process. At another point, he led a revolt among the inmates which necessitated both the Avengers' and Freedom Force's intervention. Truman Marsh goes insane over stress of the breakout, setting off the Vault's self-destruct which was going to destroy half the state (due to several mistakes), killing millions. Marsh was fully willing to kill all the innocents in order to destroy the supervillains by the time Venom kills the warden. Iron Man, Hank Pym and Thunderball neutralize the bomb. One of Venom's escapes resulted in Guardsman Hugh Taylor's death, inspiring his father to assemble a group of embittered former staff from the Vault illegally using modified Guardsmen armour to exact revenge against Venom. Vance Astrovik was sentenced to imprisonment in the Vault, after being found guilty of the manslaughter of his father.