However, instead of having a different message for the eggs, I think every egg, no matter what type, will get the same mesage. For example, "There is an adult dragon guarding this egg, and no matter how much effort you give, you are unable to see it.
Also, maybe it can work like, when you get ten dragons, 10 percent of people who view your egg will get the guarded message. When you get 17 dragons, 17 percent. Same with 30, 35, and so on. But however many dragons you get, I think the limit should be 50 percent. After all, the dragons can't do all the work.