Born in Bologna in 1939, Raviola lived there for most of his life.

Having worked as an illustrator, he started his comics career and his association with Max Bunker in 1964 with the series Kriminal. He took the pseudonym Magnus, from the Latin phrase Magnus Pictor Fecit ("A Great Painter Did It"). During the 1960s the duo became a mainstay of Italian comics creating successful series such as Kriminal and Satanik (1964), Dennis Cobb, Gesebel (1966, only first six stories by Magnus) and Maxmagnus (1968).

In 1967 they started working on a new series resulting in the May 1969 release of Alan Ford. Magnus' atmospheric use of black and white launched a new comics genre called fumetti neri (black comics/adult comics).

After leaving the T.N.T Group in 1975, Magnus began an association with Renzo Barbieri's publishing house. He devoted several years to research and the result was a revolution in the erotic comics genre. In the 1970s works like Midnight of Fire, Ten Knights and a Wizard, Vendetta Macumba and The Living Skull came out. Magnus continued creating the long saga The Outlaws and in 1975 he started the Lo Sconosciuto (a character whose lastname is Unknow, intentional misspelling of "Unknown") series, today considered one of Magnus' finest creations. In 1977 The Company of the Gallows series appeared.

During 1980s he created two heroines: Milady 3000 (1980–1984) and Necron's Frieda Boher, written by Ilaria Volpe. Milady, translated also in France on Metal Hurlant, is a science fiction series where Chinese culture, Flash Gordon and Star Wars' influences, erotism and technology are well mixed. Necron instead was a pornographic series, though Magnus' skills and humour manage to make it interesting.

Magnus briefly returned to Alan Ford in 1986, to draw the 200th episode.

Subsequently, inspired by eastern literature, he created The 110 pills, Fiori di prugno in un vaso d'oro and The Enchanted Women. In 1989 Magnus began his last work, a long story featuring the popular Italian western character Tex, written by Claudio Nizzi: for it Magnus completed 223 exceedingly detailed plates in 7 years of work, for which he used original sources for any historical element, and studied from live any natural detail such as leaves, light and trees. In August 1991 Magnus had moved to Castel del Rio, near Bologna, where he spent his last years and died of cancer just few days before completing his Tex story.