Bioshock: A Machine For Pigs

[Alardem]

Spoiler below!

A middle-aged white man, wracked with fragmented memories and on a quest to find his children, explores an enclosed environment with anachronistic technology and bizarre abominations against nature. As his journey continues, it becomes clear that the protagonist has much blood on his hands and the antagonist - a nihilistic madman with a penchant for hammy speeches and an army of mindless followers - is quite familiar with him. At one point, the society which the protagonist has become quite disgusted by is set upon by the antagonist's hordes.

It turns out that the protagonist and antagonist are one and the same - different incarnations of the same being, one a blank slate hoping to undo the error of their ways and the other driven to despair by atrocities into drowning the world in blood. The protagonist learns that he sacrificed his own children in pursuit of his goals, and ultimately learns that the only way to undo his sins is to join with his dark half and kill himself.

Booker DeWitt or Oswald Mandus?