Daughter

Daughter follows the life of a girl, born to a witch queen and a thief. Raised by her father until she came of age, when her mother appears in a royal coach to claim her. Her mother kills her father and begins the spell that will define the girls life, for every decision she makes she will become two different girls, one for each choice. As she grows into a woman she must defend herself, or strike out against her sisters, each the embodiment of the roads not taken, to ensure that she is the one to survive.

Daughter began as a neverwinter nights mod but the story soon grew much bigger and more interesting. It became a non linear story in which the salient life choices that the main character makes create alternate versions of themselves. The character could grow up to be a princess, a warrior, a farmer, or a merchant, but regardless of her choices a warrior, a farmer, and a merchant would all exist. The player would have to contest with these manifestations of the choices not made. 

The other, more cynical element of this concept is that branching storylines are often seen as infeasible to develop, especially in longer stories and larger games. So much development time can potentially go to waste when large chunks of the game will not be seen or experienced by players who play through only one storyline. The hook here is that the world unfolds very similarly regardless of your choice. Whenever a player interacts with another Daughter that interaction is reused, the only difference being which side of the conversation the player is on. But in this model such confluences are not convergent as with the string of pearls model of nonlinearity, where it doesn’t matter if you are playing good alignment or bad alignment, you will join the battle to save the city/planet/cat at the end of each level. Instead each encounter is an important turning point for both characters, respecting the players choices which lead them to the moment with an outcome that fits their story. That obviously doesn’t make the game as small as a linear story, but the efficient reuse of all the key moments within a sandbox like game world could make a wildly responsive storyline possible with a budget on par with much smaller non-linear games.