He is mostly known as the "Boss" of the gang Passione, which corrupts Naples by dealing drugs in the streets, making him Giorno Giovanna and Bruno Bucciarati's superior and greatest enemy. Because of his obsessive secrecy, almost no one knows about his appearance, name and past. Diavolo is also the father of Trish Una, and commands Team Bucciarati to bring her to him whilst keeping her safe from the traitorous La Squadra Esecuzioni.
Diavolo is secretly the alternate personality of Vinegar Doppio