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Pluto is a dwarf planet within the Sol System. It was the site of an incident with the Vex during humanities Golden Age. During the City Age, Pluto was one of many objects within the Sol System that was occupied by the Black Fleet.
During the Golden Age there was an incident on Pluto at a Clovis Bray installation which involved the Vex. The Warmind Rasputin intervened and some knowledge of the incident became public knowledge. Clovis Bray I was furious with Rasputin for drawing too much attention to the incident and the threat of the Vex, which made the public and his employees nervous about dealing with the cybernetic species.
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