Demon's Souls, spiritual predecessor of Dark Souls. In celebration of two years of mind-numbing, controller-snapping difficulty, the publisher has some special World Tendency events lined up for the rest of the month.
Starting today and running through October 17, the in-game world of Demon's Souls will switch to Pure White Tendency, which makes the game (somewhat) less difficult and even opens up certain paths and items. From October 17 through the rest of the month – just in time for Halloween – the world will shift to Pure Black which, you guessed it, makes the game even more difficult (okay, fine, it also opens up different hidden areas too).
To offer up a birthday analogy, it's like Atlus is giving everyone a cake topped with beautiful white icing and a filling made of pure evil.