The Royal Egg of the Bearers Egg

Did you mean the Character, the Character's Brother, or the Inventor that got ahold of it?

The Royal Egg is a powerful source used to create and destroy, when getting in the wrong hands can cause trouble.

Looks
The Royal Egg is just a purple egg with red horns, and that's pretty much it.

Trivia + References

 * The Royal Egg can create beings of light, known to everyone as Light-Creatures.
 * The Royal Egg was stolen by someone, who later created the Shelly-Friend we all know.
 * The Royal Egg doesn't have an age, but it has been around on an island for thousands of years.