The top of some Jewel cards depict 1 or more Crowns. Crowns have two purposes in the game.
1) Acquiring 10 crowns will end the game and
2) They will attract Royal Cards.
- Upon acquiring your 3rd Crown, take 1 of the available Royal cards and resolve its ability.
- Upon acquiring your 6th Crown, take 1 of the available Royal cards and resolve its ability.
This means, that both players can have 2 Royal cards at most.
Taking a Royal card is not an action. Place your Royal cards next to your Jewel cards.