Avatar: Dragon Eggs and the Solstice
In Episode 313 (The Firebending Masters) Aang and Zuko enter a secret chamber and discover a ‘gem’ that “feels almost alive”. This has led many fans to believe that the ‘gem’ is actually a dragon egg.
Let’s assume this theory is correct.
But if it’s a dragon egg, why would the Sun Warriors hid it here?
The obviously reason is for protection. Dragons had been hunted almost to extinction, and a dragon egg would be rare and very precious thing.
But I have another theory.
The Sun Warriors hid the egg in a chamber that could only be opened during the solstice (most likely the summer solstice). In the avatar world, the solstice is when the spirit world and the physical world are closest together and spiritual energy is at its peak. The solstice is also when the Sun is at its strongest/ weakest (relative to the perspective on earth). The Sun is the source of firebending. And since Dragons are the original firebenders, it would make sense for dragons to have some connection to the Sun and the solstices.
My theory is that secret chamber is specifically designed to hatch dragon eggs.
On the solstice the chamber would open. Then Sun Warriors would bath the egg in sunlight concentrated from the sunstone outside. The concentrated sunlight during the solstice would fill the egg with spiritual energy and cause it to hatch. (Just like how Roku used the solstice to talk to and empower Aang.)
To me at least, it makes sense that the original firebenders would be born on the solstice.