3 And another sign appeared in heaven: behold, a great red dragon, with seven heads and ten horns, and on his heads seven diadems. 4 His tail swept down a third of the stars of heaven and cast them to the earth (Rev 12:3-4).
The traditional rendering of this passage is someone misleading because it transliterates the Greek designation rather than translates the Greek designation. The original text uses the Greek word dracon. The English rendering substitutes English letters.
For a modern western reader, the word "dragon" triggers mental images that are conditioned by medieval art and Hollywood movies. The 1981 movie Dragonslayer, starring Ralph Richardson, is a good example.
But that raises the question, what did the "dragon" in Revelation actually look like? Commentators draw comparisons with OT sea monsters and chaos monsters or Greco-Roman and ancient Near Eastern mythological monsters. That, however, simply pushes the question back a step, because we still don't know what mental image that conjured up in the minds of ancient people.
There are some ancient artistic representations of dragon-like figures, such as the mosaic of the Mushhushshu "dragon" guarding the Ishtar Gate in the city of Babylon. Another example would be the Feathered Serpent in Mayan and Aztec art. Likewise, you have the Chinese iconography of dragons. This can be traced back at least as far as a Neolithic oyster shell "dragon".
But while it's natural for modern viewers to identify these examples as a dragons, the recognition is circular inasmuch as we begin with a culturally-conditioned preconception of what dragons look like. These examples just happen to bear some resemblance to our preconceived notion of what dragons are supposed to look like.
An ancient literary candidate is Leviathan, the fire-breathing monster in Job 41. In Egyptian mythology, the netherworld is guarded by fire-breathing cobras. I wonder if that's based on spitting cobras.
In the astronomical setting of Rev 12, it's quite possible that the "dragon" represents an ancient constellation. In that event, the implicit imagery either derives from the actual appearance of the constellation, or from ancient artistic depictions of the constellation.
A related issue is the question of how the idea of dragons originated. Does the prevalence of "dragons" in geographically diverse civilizations reflect cultural diffusion, or did these arise independently of each other?
In some cases these are hybrid creatures. In other cases, stylized snakes.
Here's another possibility. This is speculation on my part. To some extent, dragons might be the product of nightmares. Suppose you live in a location frequented by pythons or crocodiles and the like. That's something you might dream about. And, of course, dreams can be surreal.
In fact, one place I used to live had some big alligators in the rivers and ponds. I saw them from time to time, and I once had a bad dream about alligators or crocodiles. In my dream I was walking along a footpath between ponds or rivers infested by crocodiles. And in the dream, the area was flooded, so there was no margin between the footpath and the infested waters. I was surrounded. There was no escape.
Here's another consideration: I expect that pagan witchdoctors have nightmares that are even worse than ordinary nightmares. What if a witchdoctor lives in a location frequented by pythons or crocodiles, and the like. The fact that he's immersed in the occult will drench his imagination. Some of his dreams might be inspired by ordinary snakes or crocodiles, but that's distorted and magnified by the surreal nature of dreams, as well as his diabolical imagination. Perhaps dragons are, in part, a product of subconscious fears. There's some real information feeding into that, but other factors turn these into surreal monsters.