1) Make a 4th character that is a Dark class character - can only have 1 2) Level that character up to max level 3) Once you've maxed 4th character, new story line opens up for other 3 characters 4) Story has you chasing your 4th, dark, character across the universe 5) The finale is a showdown where you have to battle your own 4th character with the perks and loadouts you have equipped on them but its controlled by the AI...You literally fight your own creation [spoiler]and you probably get your ass kicked over and over again[/spoiler]