I have noticed while playing that sometimes there is a loud cracking noise and my character glows white, after which I get an additional Estus Flask. Why is this happening? Is it related to being near areas where there are bosses?
Example: I idled right before the entrance to the Gaping Dragon boss fight. During that time, I gained two Estus Flasks for a total of 12.
Another time I was fighting one of the knights in the Undead Burg church below the Bell Gargoyle area when this happened.