Well, first of all, the association with Hercules' labor is a key element. He fought the Nemean Lion which then became Leo. The shape of the constellation is also important. It's not just a random pattern but clearly a lion. Also, the role it has played in different cultures' stargazing and astrological beliefs over time. For example, in some cultures, it was seen as a symbol of strength. And of course, the stars within it, like how they are arranged and their relative brightness, are all parts of the main elements of the story.
The main element is the Nemean Lion from Greek mythology. It was a great and terrifying beast that Hercules had to face. Another element is the shape of the constellation, which resembles a lion. And the star Regulus is also a significant part as it is the brightest in Leo.
The main elements start with the mythological aspect. The Nemean Lion was no ordinary lion; it was a monster. Hercules' encounter with it was a heroic tale. This encounter led to the creation of the Leo constellation. Then there's the physical aspect of the constellation. The stars that form it are an element. They are grouped in a way that gives the appearance of a lion. Also, the fact that it is a zodiac constellation adds to its significance. People have associated it with certain personality traits in astrology. And its visibility in the night sky at certain times of the year is another important element in its story.