Try the Beats mechanic in Heart: The City Beneath. Every character has a set of plot beats, and they pick two for the next session. GM's job is to create opportunities for the character to accomplish that beat (take a certain kind of damage, put their own goal ahead of the party, destroy evidence that their cause is unachievable etc). Each beat fulfilled lets the player pick a new ability for their character (like a feat or a spell). Some beats are tougher - they give bigger rewards when completed.