Hrumph. Grumpy. As always. Such a surprise. Do I take it out on my PCs? Not really, surprisingly. However, I also am the type of DM to throw more at them then they by rights can handle.
However, in this case, the adventure I made that the group is currently embarked upon can potentially be a TPK. Total Party Killer. There's some really deadly stuff. And some of it is probably a bit unfair. I changed the way I play. Totally.
I've done things that I don't normally do. Traps. Which I always thought were kinda stupid. I mean who puts a pit trap where you pass by when you go to the bathroom in the middle of the night? That's just stupid. This game, traps are tactical. They aren't there just to wear down the party. Where they are set up are intentional to put a difficulty for those who are attacking.
This campaign is more like urban combat rather then traditional medieval combat. Even small threats are more deadly. The Orc in a 10x10 room whomped off half of Megan's HP. I hate to think what would happen if they met up with a clan of Kobolds. Things that are experts at traps and small quarters combat. It would be a bloodbath.
That being said. There's going to be a point where they have to run. Probably two. They might run at the first, which isn't really the point they need to run, the second though, if they stand and fight, they WILL die.
If that happens, well, they get to go back down the hole with new PCs. However, it will be different. I almost always start my PCs off at 3rd level with 2700 GP to spend how they want. However, if I get the TPK, well, then they'll start off with a handicap. Still at 3rd level, but only starting cash. So just starting equipment. Harsh, I know, but if I allow them to kit out, then well, that's WAY too much treasure. So just enough to get started.
However, I doubt any of the stuff that's really useful will still be there though. These dungeons are living entities. Smart critters take useful stuff. And there is one creature that will be exacting revenge. It will take some doing to keep it alive, but it will be fun. Not the Big Bad, but a reocurring villian. Someone to show up and cause problems. Kill someone and run away. Dragging the body with all the treasure as well.