It is the most common puzzle found in a dungeon. It is also the most common obstacle, and a source of great frustration. What is it?

Answer: A door.

Is it locked? Is it trapped? What’s on the other side? Is it real?

I made a hypothetical “dungeon character sheet” to advance my dungeon design cause. I took my character sheet — posted a few weeks ago — stripped it of stuff that only characters can do, and filled it in with my notes and gobbledygook.

Then I started asking myself questions. That’s how it starts.

I left room for defenses. On a character, they’re AC, Fortitude, Reflex, and Will. On my dungeon sheet, they were blank because I didn’t know what they should be. If you attacked a dungeon, what would prevent you from succeeding?

Let’s say “attacking” a dungeon constitutes plumbing its depths and robbing its secrets. Its first line of defense are its doors. When you get right down to it, doors could be any kind of selectively-passable barrier.

Maybe it’s an electric fence. Maybe it’s a Whomping Willow. Maybe it’s invisible and you have to speak “friend” to enter. Whatever. It’s a door.

But not everything uses doors. What if you don’t want to go through the door because it might be trapped? Well, if you were a character with a really high AC, I’d say go for Reflex or Fortitude. It’s less common but still viable.

The next line of a dungeon’s defense are its walls. You can straight-up break down these impassable barriers — whether it’s hacking through foliage, cutting oozing, alien carapace, or boring through a ship’s bulkhead. It’s a wall.

After walls are traps — whether it’s mud or quicksand, a tripwire alarm, a slippery waterfall, a covered pit full of spikes, a rolling boulder, or a tomb that fills with sand or water — traps are there to make life hard. It’s that easy.

Sometimes a door is actually a trap. Sad but true.

Finally, a dungeon may have a number of floors — spreading its threat across multiple levels to lure adventurers in “too deep to turn back.” This is the slow grind that wears adventurers down and leaves them vulnerable.

When it comes time to navigate the labyrinth, its floors are what makes it difficult to leave. (If there was ever a time for a “map check,” it’s here.)

I’m going to continue developing this idea and see where it goes.