My classic example was a 2E game run by a DM still in a 1E mindset. The ranger blew her tracking skill big time trying to find a baby black dragon. We found a rather large green dragon instead. It was sleeping. WE SWAM AWAY! (It was an underwater lair.) Eventually we went back to kill it only to find it wasn't a green dragon after all; it was the discarded scales of a dracoliche!talozin wrote:Okay, I'm going to yeah-but you here. Yeah, but if the characters decide they're going to go to the dragon's lair, you, as the DM, should be interposing encounters along the way to ensure that they are at least potentially capable of dealing with it by the time they get there. "Dealing with it" may equate to "realize we're in way over our heads and run away", or it may equate to hearing the lamentation of the Dragon Women. It just needs to not equate to "rocks fall, everyone dies."
TPK sucks, no doubt about it. But living without the fear of TPK is not living, and is unfun. Wasn't that the whole idea of points of light? It's a dangerous world out there. You should be surprised every day that you didn't die the previous day. When you realize that every encounter is level appropriate just for you, the world becomes a bright monochromed place; flavorless, but far from dangerous.