If it’s not enough to have Argus with his hundred eyes, some figures in classical mythology had to have more than one face. As the face is often equated with character, this enabled them to behave in two contrasting manners, as if they were more than one person. For the visual artist, that required their multiple faces to be quite different.

This is most apparent in the god Janus, who traditionally is thought to have given his name to January, the first month of the modern year. There are at least two problems with this: January wasn’t the original start of the year for the Romans, who like many cultures used to begin the New Year in Spring instead. By the time that more modern names were given to the months, though, it started with Ianuarius, which was supposedly named after Janus. The other problem is that it’s even disputed whether Ianuarius is derived from Janus, or Juno, who in some ancient almanacs was awarded the month instead.

Nevertheless the association between the start of the year fits well with Janus, who’s classically depicted as a duality, with two faces on a single head, one looking backward (to the old year), and the other forward (to the new): Ianus Bifrons in Latin.

So he appears in Anton Raphael Mengs’ wonderful fresco in the Vatican’s Camera dei Papiri, The Triumph of History over Time (1772). Father Time with his long grey beard and scythe is in the foreground, and behind him History is busy keeping records. She looks up to the fresh new face of Janus, as the old one looks away to the right.

For all his importance in the ancient city of Rome, Janus has hardly been painted in more modern times. This is because he doesn’t appear in major references to myths, such as Ovid’s Metamorphoses, sources used by artists from the Renaissance onwards.

He does, though, appear as the occasional statue. In Nicolas Poussin’s brilliant Dance to the Music of Time (c 1634-6), opposite the dancing figure of Pleasure is a small herm of Janus, whose two faces look to the past and the future.

Janus’ association with gates, and the start and end of war, gave rise to an interesting tradition in classical Rome: the gates at each end of open enclosures associated with the god were kept open in times of war, and closed when the city and empire was at peace. Opening the gates therefore became a mark of starting a war, as used in Peter Paul Rubens’ paintings from late in his career.

In his Temple of Janus from 1634, those gates, here imagined to be those of a temple, are being opened to let a warrior through to battle. Above that doorway is a statue of Janus with his two faces.

The goddess Hecate is more complex, as her most distinctive feature in most visual representations is the fact that she is triple-bodied. Each of her three bodies is complete, and her three faces look outwards.

Francesco Primaticcio’s drawing of Diana and the Tripled-Faced Hecate with Pegasus from the sixteenth century is unconventional in showing her as three-headed, and with butterfly wings. She’s kneeling at the head of the winged horse Pegasus, opposite the huntress Diana, with whom her myths became confounded.

Stéphane Mallarmé’s drawing of a classical sculpture of Hecate, Greek Goddess of the Crossroads was engraved for his illustrated account of classical mythology published in 1880. This is her most conventional representation: fully triple-bodied, holding a key at the left, and torches to the left and right, with a symbol of the moon on her forehead.

Two faces can also appear on figures representing personifications such as Deceit.

In Annibale Carracci’s Allegory of Truth and Time from 1584, the winged Father Time, who lacks the scythe he’s most commonly associated with, is putting his shoulder to Truth to raise her from the well. She’s clutching a mirror in her right hand. Trampled under the feet of Truth is the strangely chimeral two-faced figure of Deceit, coining the epithet two-faced.

Various monsters have also been given multiple heads. Most famous among them is the guard-dog of the Underworld, Cerberus.

Cerberus is the horrifying three-headed canine monster shown in Blake’s late illustrations to Dante’s Divine Comedy, painted between 1824–27. This refers to Dante’s Inferno, canto 6 verses 12-24, where Dante and Virgil enter the Third Circle, in which gluttons are punished. Blake is true to his source, except that he adds a cave to signify the weight of the material world.

Cerberus is a good example of the redeployment of pre-Christian mythology into Christian beliefs: it was originally the guardian of the Underworld, and prevented those within from escaping back to the earthly world. It even features in the twelve labours of Heracles (Hercules), in which he captured the beast. Dante, with Virgil’s explicit involvement, incorporates it into his Christian concepts of the afterlife.

Joseph Anton Koch’s fresco of Cerberus from 1825-28 is another vivid example.

Although there are many other many-headed monsters, I finish with another involved in the Labours of Heracles, the Lernean Hydra.

In this painting from 1876, Gustave Moreau refers to Heracles hunting this Hydra in the marshes of Lernea, near Argos, and destroying it. The Hydra was a poisonous monster with the body of a dog and multiple serpent heads, whose breath alone was capable of killing. Although he doesn’t show its dog-like body here, Moreau shows its heads according to the letter of the original story, with the marshes seen behind. Heracles is shown confronting the Hydra, with a charnelhouse of remains of previous victims at its base.