|Here Comes the Bogeyman - Francisco de Goya 1797|
When do you bring out the bogeyman? Well, if you want to make it most effective, you unleash the bogeyman on your party when they're not expecting it. For example, everyone sits down to the nth in a series of delves into whatever mega-dungeon or mega-wilderness you've been running. If the party is in the midst of something mundane (i.e. heading back to town, heading back into the wilderness, resting int town), it's probably the best time to inflict the bogeyman on them. The initial encounter does not need to be deadly (unless players don't take the hint of "nothing seems to be harming it"), but should scare the crap out of them and send them running.
Now you've just shifted the campaign and put the players on the defensive. What they hell is that thing? What does it want with us? Why don't it go away? How do we stop it? These are the themes of the bogeyman sub-campaign - essentially a horror that the players didn't ask for, but which they now must deal with.
Tomorrow, I'll discuss some of the specifics of the bogeyman ...