Draco
The constellation of Draco "The Dragon" seems to only be spoken of from the ancient greek and roman periods. A long line of stars makes up this weiving dragon around the Little Dipper. This serpent-like creature sits between the two Ursa constellations, yet in the modern sky, with light pollution appears very dim.
Greek/Roman legend
The constellation Draco is associated with several myths, most frequently with the one about the 12 labours of Heracles, represented by the neighbouring constellation Hercules. In the myth, Draco represents Ladon, the dragon that guarded the golden apples in the gardens of the Hesperides.
The golden apple tree was a wedding present to Hera when she married Zeus. She planted the tree in her garden on Mount Atlas and tasked Atlas’ daughters, the Hesperides, with guarding it. She also placed the dragon Ladon around the tree so that the Hesperides would not pick any apples from it. In some versions of the myth, Ladon had a hundred heads and was the child of the monster Typhon and Echidna, who was half woman and half serpent.
In others, he was the offspring of two sea deities, Ceto and Phorcys, and there is no mention of the number of heads he had. As part of his 12 labours, Heracles was asked to steal some golden apples from the tree. He killed Ladon with his poisoned arrows and took the apples. Saddened by the dragon’s death, Hera placed its image in the sky among the constellations. Draco is usually depicted coiled around the North Pole, with one foot of Heracles on its head.
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In Roman mythology, Draco was one of the Giant Titans who warred with the Olympian gods for ten years. He was killed in battle by the goddess Minerva and thrown into the sky, where it froze around the North Pole.
https://www.constellation-guide.com/constellation-list/draco-constellation/
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Conclusion
Draco appears to be used for many different stories throughout greek and roman history. Where the 'true' story lays I believe isn't an issue, as these stories would have been told and passed on by word of mouth more than written word. I also feel that the image of a serpent or dragon which stays in the night sky all year round is useful for legends told, as it seems there to always be a mythical beast which requires slaying for a heroic god to prove themselves. Where exactly this might sit in a moral ground for storytelling I'm not sure, but it has some weight to show that in order to have a good character, we need a bad.