Frederico was the Italian business partner of Jacobi Sporachi. Jacobi hired him to help him run the Sporachi family business of pearl harvesting, because Jacobi was a young man and inexperienced in business matters. When the pair found a flawless black pearl, it turned out to be cursed. Frederico was driven insane by it, and became a monster.
Using his newfound power, Frederico cursed Jacobi to eternal life without eternal youth, and subsequently took over the Sporachi family mansion in Venice. Over the ensuing centuries he became further corrupted by the pearl's power, becoming a hideous beast that was a part of the house itself. He would gain power and life by consuming other peoples' life forces, either by absorbing their physical forms, or killing them outright.
He was destroyed for good when Jonny Quest smashed the evil pearl.