Hero, Captain, King: Adventures in a Changing World

From the Game's Introduction:

Hero, Captain, King is a GM-less roleplaying game where the players create epic adventures for each other and together develop a fantasy world that grows and changes during play.

General Flow of the Game
The players begin by creating a world (or using a pre-existing one) to play in. This world is then threatened by a series of crises and the players take on the roles of the heroes trying to save the world. After a crisis has passed the players make a series of rolls to see how the world changes until the next crisis arrives, continuing to play the same characters or creating new ones depending on who are still alive and fighting for good.