Sclavi is most famous as creator of the comic book Dylan Dog in 1986, for Italian publishing house Sergio Bonelli Editore.

It has been in collaboration with several artists, including Claudio Villa, Corrado Roi, Gustavo Trigo, Carlo Ambrosini, Luigi Piccatto, Angelo Stano, Mike Mignola, Andrea Venturi, Giampiero Casertano and Bruno Brindisi.

[4] In the same year, he joined the redaction of Corriere dei Ragazzi as editor of the column Sottosopra[6] and here he met Alfredo Castelli, with whom he collaborated as Ghost Writer for the comic series Gli Aristocratici ("The Aristocrats"), writing the screenplay of some episodes and later creating his own characters like Altai & Jonson[3][2] drawn by Giorgio Cavazzano.

[4] He collaborated with other newspapers belonging to the Corriere della sera group and with the journal Amica (where he edited a humour column) and with Salve (where he wrote as film critic).

During the same period, he wrote also Tre ("Three") and Mostri ("Monsters"), published ten years later despite Natalia Ginzburg had already noticed him to the Giulio Einaudi Editore.

[7] When Corriere dei Ragazzi was closed in 1977, Sclavi began to collaborate with Il Corriere dei Piccoli, writing comic series like Allister, Miki, Fantòm[4][6] alongside Sam Peck, Johnny Bassotto ("Dachshund Johnny"), Il Cavallino Michele ("Michele the Little Horse"),[4] La guerra nell'aria ("The War in the Air") and Le pagine della Befana ("Befana's pages").

[4] Among his first works, he had written screenplays for Ken Parker (the issue #35 Il sentiero dei giganti and #41 Alcune signore di piccola virtù, both based on scripts by Giancarlo Berardi)[6] and then Sclavi had replaced Guido Nolitta for Zagor.

It was later propose to place the story in London after a discussion with Bonelli, because in New York there was Martin Mystère already and England seemed to be more ideal for horror due to its ancient traditions.

[14] The creation of the character began a year before when Sergio Bonelli, owner of the publishing house, and Decio Canzio, general director, preferred to return to work on traditional comics and eventually to create new ones.

The novel Dellamorte Dellamore had a wide success and in 1994 Michele Soavi directed a film based on it (distributed in the US with the title Cemetery Man) starring Rupert Everett, the actor who inspired the somatic traits of Dylan Dog.

From this point, stories signed by Sclavi had lost their splatter feature of the first issues and they began to focus more on the surreal and grotesque, with incursions in social and science-fiction themes.

[6] During the eighties and nineties, aside his main activity for Bonelli, he collaborated with other publishing houses: between 1982 and 1984, he wrote Agente Allen ("Agent Allen") and Vita da cani ("A Dog's Life") for Il Giornalino,[4][17] and, from 1987 to 1991, Sclavi published on Comic Art three stories of the Roy Mann series[4] drawn by Attilio Micheluzzi and in which he tells the adventures of a comic screenwriter who, due to the explosion of a coffee-pot, is catapulted in a parallel universe.

[18][6] Some characteristics similar to those of Dylan Dog and in some novels of Sclavi can be found in Roy Mann, but with more influences of humour, fantasy and paradoxical elements.

[4] In 1993 the book Nel buio ("In the darkness") was published a collection of ballads in the style of Francesco Guccini, Fabrizio De André and Claudio Lolli: these are not poems as evidenced by Slcavi himself, but compositions born to be set to music.

Some of them, I miei sette figli ("My seven sons") and Sotto il segno della volpe ("Under the sign of the fox"), have become songs sung by Tiziano Cantatore in the album È sparita l'orsa maggiore (Eleven, Fonit Cetra, 1978).

[4] Since this moment, he had stopped to write novels until the second half of the nineties, when he published Le etichette delle camicie (1996) and Non è successo niente (1998).

The character of Dellamorte represented for Sclavi a general test for Dylan Dog because he confronts a horde of zombies along with a grotesque sidekick, Gnaghi, and he builds a scale model as hobby.

[3] It is an autobiographical novel where Sclavi tells about himself through three characters: Tiz, successful screenwriter, Tom, a depressed alcoholic in a creative crisis and with suicidal temptations, and Cohan, who represents Sclavi at the time and has reached an equilibrium and an affective serenity, but he has lost his creative vein; other numerous characters around the main ones can be reconducted to colleagues in Bonelli with a representation of life in the redaction.

[2] Sclavi wrote also for the publishing house for children La Coccinella[4] and in 1999 he took part to the realization of the video-game Dylan Dog Horror Luna Park.

[23] Sclavi is a member of CICAP (Comitato Italiano per il Controllo delle Affermazioni sul Paranormale, Italian Committee for the Investigation of Claims of the Pseudosciences).

In another case, the one of “Nero.” (with the full stop, notice that), a film directed by Giancarlo Soldi, I had written personally the screenplay (that I had later transformed in a novel), and then I can't make any judgement.