Initial thoughts
This concept started with eggs. I wanted to paint some golden eggs. Then I thought glowing golden eggs could be more interesting. Next, eggs should be in nest. To make a story scene I prepared a snake around the nest so it had some tension between these two parties. However, I was not satisfied with the snake composition. It was either too small or away from focal point. It didn’t feel like a threat to eggs. I even tried to put in a snake hunter animal such as mongoose to indicate that the snake was trying to steal the eggs.
No, I didn’t like that either.
After struggling a little bit and searched tons of snake photos online, I decided to scale up the snake as much as I can. It suddenly gave the fairy tale feeling. A giant blue serpent looked at several glowing eggs in a nest. At this point, I still believed that the serpent was trying to steal the eggs. So I added an iron cage in order to protect those eggs. As soon as I put the cage in, the story changed. Now the eggs might be the serpent’s. The giant snake could be somehow glowing too. Someone else stole its eggs and put them in a cage in order to lure the mother serpent closer. One smaller egg rolled out of the cage and hatched. Once the baby serpent escaped, the egg shell had no glow at all.
Digital sketch
The purpose of the hatched egg is to tell what is actually glowing, the snake (inside), not the egg shell (outside). The serpent’s glow comes from underneath its scales, same golden yellow as the unhatched eggs. Whole color theme of this piece is teal and yellow.

Summary
I first mixed the gold pigment with gold paint together and painted the edge of scales. Later I noticed that I still needed to tone it down with some color glazing. Otherwise the gold paint was to shinny.
Well, whoever put the eggs in cage is not a bad guy I assume. Might be he/she just want a closer look of the giant blue serpent that hides in the thorny woods all the time. Once hatched, the baby serpent can easily get out of the cage and reunite with their mother. ❤