The technology for Exo-armour was originally developed during Mankind's Dark Age of Technology. These sealed environment suits enabled maintenance crews of spacecraft to operate in extremely hazardous environments such as hard vacuum or in other adverse atmospheric conditions. During the Great Crusade era of the late 30th and early 31 st Millennium, the Mechanicum was receiving a steady influx of new and rediscovered technologies from each planet brought to Imperial Compliance, and, in an effort to stem the horrendous loss of Legionary lives resulting from the ferocious conquests, attempted to design the "ultimate" pattern of Power Armour which would render a Space Marine virtually invulnerable. The design emerged from a hybrid of standard Legionary Power Armour, the cybernetic shell of a