Melchior, a deranged super mutant, hails from Redding, where he earned a living as a miner and entertained the community with his magic tricks on the side. In an event witnessed by his young son Melchior Junior, he was kidnapped by the Enclave, and taken to the Mariposa Military Base where he was turned into a mutant and has since taken leadership of the second generation of super mutants.
Whether he masterminded the rebellion against the Enclave slave masters is not known, but his magician skills were almost certainly used to accumulate and hide weapons, even though as a human his tricks were limited to pulling rats out of a hat.
Melchior is the boss character of Mariposa Military Base. The Chosen One should approach Melchior with caution as he will summon other monsters from the goo to attack. The monsters he summons are: four deathclaws, four floaters, four fire geckos, and four mole rats. Melchior will summon monsters until there are four in total, and if any are killed he will summon more to maintain this number.
Surviving and killing all waves of his pets without killing Melchior results in humorous dialog. "Uh oh, me outta furries to moottate."