Your goal is to reign for as many years as possible. Once your reign ends you continue to rule; however, it’s as the heir of the previous king.
During these many reigns, your choices will complete royal deeds (which grant a title), as well as unlock new characters and decision cards. There are even multiple death cards to unlock. Touch on the castle icon in the upper left to check your progress. Each time you uncover something new, a star appears next to the castle icon at the top of the screen.