Two headed or two-faced creatures from myth, fiction, and symbolism.
Birds and Animals
The Amphisbaena (a.k.a. Anphivenais) a creature like a snake or a dragon with a head at both ends of its body. It is sometimes shown with wings and/or legs. Wearing an Amphisbaena was thought to help a woman become pregnant. The amphisbaena is said to have been born from the blood that fell from the head of Medusa after she was killed by Perseus. The suborder of 'worm lizards' go by the name of "Amphisbaenia" and may be the the origin of this mythological animal, because their head and tail have a very similar appearance. Alternatively, it may have been inspired by rare cases of 'axial bifurcation' which can result and lizards with a head on each end. Lizards as an inspiration would be more consistent with some of the later depictions of amphisbaena in bestiaries or as church grotesques show them with two- or four legs.
Other types of two headed serpents exist on other cultures, such as the sillhqey. And in ancient Egyptian myth a two-headed serpent called Nehebkau guarded the entrance to the underworld.
In Ghanian symbolism a two-headed crocodile (a.k.a "Siamese crocodile" or "crossed crocodile", with a shared stomach) is used to represent unity between diverse people, but also how people can fall into conflict even when cooperation is in their best interests. (For example: Adinkra stool)
Two-headed dragons are found in art ranging from ancient Mayan to present day. In Chinese mythology there is a two headed creature resembling a dragon that is known as the hong or jiang.
The two-headed eagle is common symbol of the Holy Roman and and Byzantine Empires. The two heads represent a country or empire ruled over by two powers. For example a ruler who is deemed to have both religious and governmental authority (church and state). This symbol was exported to other cultures directly. However the Incan symbol of a two-headed condor most likely has a different origin.
Hindu mythology describes a two-headed bird called the Gandaberunda or Berunda (sometimes shown with a human body) , which represents the most destructive form of the god Vishnu/Narasimha. It appears in many official crests and temple sculptures. The Gandaberunda possessed incredible strength. and It is sometimes depicted carrying an full-grown elephant in each of its claws.
A two-headed jaguar appears in some ancient Mexican art. (Sometimes described as a lynx, or just a cat).
A double-headed lion appears in heraldry and in decorative arts (for example in the architectural decoration inside the George Washington Masonic National Memorial). However it does not seem to have a particular known symbolic meaning.
A two-headed hound was said to watch over the cattle of a giant called Geryon. This hound, called Orthus (or Kyon Orthros) was the father of the Spinx and the Nemean Lion and older brother to Cerberus the three-headed dog of the Hades. When Hercules stole the fabulous catte he killed their caretakers including Orthus, his master Geryon and the other herdsman Eurytion. (Orthus appears in the game Titan Quest). Orthus is sometimes shown with a tail in the form of a snake. Orthus is best known today as the logo for the music television station MTV.
North American art sometime depicts a two head form of the raven called the split raven.
A god of the Aztec, Quetzalcoatl, is sometimes depicted as a two-headed, feathered serpent. Serpents appear throughout Aztec mythology for example in the Xiuhcoatl (Fire Serpent), Mixcoatl (Cloud Serpent) and Coatlicue (She of the Serpent Skirt). The two heads sometimes represent the earth and the power of natural disasters. Double-headed serpents appear on ornate ceremonial objects that were probably worn over the chest during important rituals. An example of a beautiful mosaic chest piece can be viewed at the British Museum. Quetzalcoatl is the symbol of the Aztec football club.
Other less well-known two-headed creatures with enigmatic base species appear in artifacts from Africa and Patagonia.
The pushmi pullyu is a purely fiction two-headed llama from from Doctor Dolittle. But it may have been inspired by a real mythical creature that was thought to be an omen of illness. For example there is rock art in Chile showing a two-headed llama.
Agni is an Indian God of fire often depicted with two heads and accompanied by a ram.
Janus (a.k.a. Ianus) is the two faced god of doors and gateways. He was deemed able to see into both the past and future. the month of January is named after Janus.
According to some antisemitic conspiracy theories, Mammon Ra is a god of wealth and prosperity, and is shown as having two bird-like heads.
Da Vinci sketched an allegory of Pleasure and Pain as a two-headed man.
In the Hermetic/Alchemical belief system the deity was often shown as having two heads, on male and one female (Sol and Luna).
A number of other cultures have produced two-headed human figurines whose meaning is now not fully known.