Royal Dragons are the shiny breed of dragons and can be obtained by breeding two dragons who have the Frost Breath, Poisonous Breath, and Shock Breath traits between them. You can also obtain one by trading it with another player or check an unchecked Royal Dragon egg however in order to unlock the ability to breed it you need to have all three breath traits present in the pair of dragons your breeding to unlock it. Having a Glistening/Radiant/Sparkling trait gives a boost to get a shiny breed however for Royal Dragons, the 3 BREATH TRAITS ARE NECESSARY. Hope this helps. Good Luck