When I write my own adventures, I find that the “large scale” writing—the NPC’s, the factions, etc.—comes relatively easily for me, but the “small scale” writing—maps, rooms, and the content within (namely, the important stuff)—is more difficult. This generator makes dungeons big enough for at least a single session, and fast enough that you could theoretically improvise the dungeon during play (although I would still recommend preparing the dungeon beforehand whenever possible) depending on how familiar you are with reading your tarot deck. Plus you get to roll a bunch of dice right on top of your tarot cards which gives me a thrill every time.
First, deal out nine tarot cards in a 3x3 grid. To me, the true spirit of a dungeon is hidden in the wandering encounter table; so, before starting in with maps and rooms, take a moment to fill out a d6 wandering encounter table with the grid of tarot cards. I like to read multiple cards at the same time—I believe that cards in a well designed deck "talk" to each other in interesting ways when read in clumps. Use the three cards in the top row for the first wandering encounter entry, the middle row for the second entry, the bottom row for the third entry, the right-most column for the fourth entry, the middle column for the fifth entry, and of course the left-most column for the sixth entry. Remember that a wandering encounter doesn't need to be a monster—it can be someone to talk to, an interesting environmental factor, a mysterious event, and so on. Of course, if you’re improvising a dungeon, you can skip this step for now until you need a wandering encounter.
Now take nine dice and drop them on top of the tarot cards. If any spill outside the grid, just drop them back on the grid. Next, drop an additional number of dice equal to the number of “1’s” you rolled. Make sure that you rolled a good mix of numbers: you want at least one die in the 1-2 range, one in the 3-4 range, and one in the 5-6 range. No value should come up more than three times; if you have more than three dice with the same value, re-roll the extra.
On your sheet of paper, make a note of roughly where the dice landed with circles, and then sequentially number them. Connect the circles with lines to form a graph. No need to over-think it—it should be relatively obvious which circles connect to which. A good graph will have three or four interconnected loops and a dead end or three. Put an "S" on a line or two to indicate a secret door of some type between two circles.
This graph is your dungeon map. Each circle is a room or a hallway junction with something interesting inside, and each line on the graph is an empty hallway. I call this dungeon generation method "The Magic Tree" because the graph, um... looks a bit like a tree when its done.
Now the fun part—putting interesting things in the circles of your graph. Each circle is a room of the type rolled on the circle's corresponding die according to this table:
1. "Blank" empty room
2. "Detailed" empty room/possible dungeon entrance
3. Obstacle room
4. Treasure room
5. "Talky" monster/NPC
6. "Fighty" monster/NPC
Read the tarot card on which the die landed to determine what is actually inside the room. If the die landed in-between two cards, read both the cards to find your answer. While reading the cards, keep balance in mind. If you rolled a lot of treasure rooms, they might be smaller treasures or the real valuable treasure might be well hidden in the room. If you only rolled one monster, make it a doozy.
That is essentially the entire generator, but here is a greater description of each type of room along with some questions to think about when reading the tarot card.
"Blank" Empty Room—these are the rooms that only have one or two things in them—your "there is a table and a few chairs in this room" kinds of rooms. Keep in mind that even the barest of rooms tell a story!
What furniture is in this room? What does it smell like? How is the room decorated? What plants grow here? What color are the walls?
"Detailed" Empty Room—these are the empty rooms that might not have any obvious obstacles, but still tell a story. There is usually a thing or two in this kind of dungeon that players can interact with—a chest to open, a window to inspect, a mysterious glove to examine.
Who uses this room? What did they leave behind? What's in the chest? What happened in this room? What is the interesting thing in this room?
Obstacle Room—these rooms contain some sort of trap or obstacle that the players have to use their wits to overcome. A good obstacle doesn't need to be riddle with a "correct" solution—its your job to get the PCs into trouble and their job to think their way out of it.
What is the obstacle in this room? What does the obstacle hide? Is the obstacle a hidden trap or an obvious impediment? is there a trick to the room? How do the people who live here get around this obstacle?
Treasure Room—these are the rooms with the good stuff: treasure. Keep in mind that not all treasure lays about in heaps on the floor. Sometimes great treasure might not be obvious—the powerful sentient broom might be haphazardly leaning in the corner, ironically caked in dust.
What is the treasure in this room? Where is it? How much of it is there? Is it magical? Is it hidden in the room?
"Talky" Monster/NPC—these rooms contain the kinds of monsters that are at least sentient and able to talk...if they chose to do so. They might have their own goals and motivations that players can leverage to their advantage.
What does the monster/NPC want? Is it something the players have or want for themselves? How many of them are there? Why are they in this room?
"Fighty" Monster/NPC—these rooms contain monsters/NPCs that are either not-sentient or not willing to talk. "Fighty" monsters aren't just there for players to use the combat chapter of the Player's Handbook—they're there to make the dungeon dangerous. There's no reward without risk.
What makes this monster interesting? Is there anything interesting in the environment that could be used in the ensuing combat? How does this monster fight? Why does this monster fight? Is there something interesting that the monster guards?
I was hoping to write an example dungeon using this method, but I underestimated how involved this post would be. In any case, I hope that this simple generator is useful. Many thanks to Logan Knight for his many, wonderful die drop generators.