If you don't play D&D, you may not realize that life, death, and various states between depend upon the roll of the dice. Most importantly the 20-sided dice peculiar to the game. According to Wikipedia, such dice produce "uniform distribution of random percentages" and "can closely approximate the real probability distributions of the events they simulate."
In other words, what happens is not the whim of the dice gods but clear and simple math. HA! As any number of Forgotten Realms authors can tell you, the dice have their moods. There are days that they dislike you, there are days that they hate you, and there are days that they chortle together in their little velvet bag while plotting your defeat.
Doubt what I'm saying? Check the answers of these veterans of the dice's malevolence when asked this simple question "Do your dice hate you?"