Royal Challenges are the ways that dragons decide who the next queen of the tribe will be, involving a challenge from a Sister, Daughter, Niece or Granddaughter, then a fight to the death between the current queen and the challenger. Only two royal Challenges have been witnessed in the series, in Escaping Peril, where Tourmaline/Ruby challenged Queen Scarlet for the Throne officially, and in The Hidden Kingdom, where Glory challenges the current RainWing Queens. It was also mentioned in The Lost Heir that Orca challenged Queen Coral, but was unsuccessful. At least in two of the tribes, challenges appear to be a public event, allowing other dragons to spectate the match while the challenger fights the queen for the throne. These two tribes include the Skywings and Rainwings.
It is unknown how exactly the Sandwings , Icewings, Mudwings, Seawings and Nightwings go through their challenges and what the specific rules are, but they are most likely quite similar to how the other tribes do them.
RainWings, unlike most other Tribes, turned their royal challenge into a game of some sorts. They used to fight for the throne like every other tribe, however, they changed it so that it would fit in with their philosophy. Instead of a fight, the queen being challenged chooses a competition that shows how well RainWings can use their natural talents, such as a venom shooting contest, a camouflage, as well as a few others. A RainWing royal challenge was witnessed in The Hidden Kingdom between Glory and the five now-previous queens, Magnificent, Grandeur, Fruit Bat, Dazzling, and Exquisite.
-Only a daughter, granddaughter, aunt, sister, or niece of the current queen can challenge for the throne. Sister-in-laws and cousins can not try for the throne.
-The fight must end in the death of the current queen in order for the princess to become queen, no exceptions.
-Male dragons (i.e. sons, brothers, uncles, and nephews of the queen) cannot challenge for the throne, nor do they seem to have much power over decisions in the kingdom.