Building a Dungeon from the Ground Up

Alright, lets make a level 1 dungeon adventure, a medium sized complex with 20 rooms.

I don't really have any huge inspiring ideas for a dungeon, so I roll on my random dungeon adventure tables for inspiration.

I get a 4, a 6, another 4, and a 3, meaning that my dungeon is a complex of secret tunnels built by pagans, rumored to contain treasure, and people know about it because someone was kidnapped and taken there, but escaped. The beings that currently live there is a group of bandits.

That's a pretty decent starting point for an adventure, you can get some role playing with the victim who escaped, and give the PCs a general idea of who they're up against before they even set foot in the dungeon.

Lets say the escaped kidnap victim is a man named Ralph, and that he was waylaid by bandits while on his way home from his butcher's shop. He says there is another victim kept there, a mute child dressed in noble's clothing, along with some coins. He says the bandits' leader had a glowing necklace that caused him to be paralyzed.

Already we now have a magic item, and an NPC. For a 20 room dungeon, we need 6 combat encounters, 6 empty rooms, 4 traps, 2 NPCs, 2 Special Rooms, and 2 Magic Items.

Of these we currently have 1 NPC, and a magic item.

Lets make the special rooms next, as they tend to be the hardest part. Since this is an abandoned pagan underground tunnel network, I think some folk magic would be the best fit for these. The first special room can be a statue of a god with antlers and 4 arms. If one places something important to them onto the statue's lap, the item disappears and they become blessed with superhuman strength, along with growing some small antlers out of the top of their head.

The second special room has a small underground stream, that glows faintly. If one drinks from the stream, they either regain 1d6 health, or become violently ill, taking 1d3 damage and a -1 penalty to attack rolls for the rest of the day. Roll a d6 to determine which occurs (evens is 1d6 health, odds is violent illness).

Now that the special rooms are done, we can move on to the traps, which to me are the second most difficult things to come up with. Lets say we have a chest with a poisoned latch on it (the chest can contain our second magic item, a potion of healing), an otherwise empty room with a tripwire connected to a crossbow, a rug covering a hole with spikes on the bottom, and a tripwire that causes a rock to fall on the triggering character's head.

Now we need the NPCs, for which we will use the kidnapped young noble-boy and the leader of the bandits. The bandits' leader has his own room, where he is looking over old maps, planning the next place to strike. Her name is Barbara, and she is gruff and has an eye patch. She will attempt to convince the party to join her bandits, and she has a magic necklace that causes paralysis.

The noble-boy has a name, but is unable to speak, so cannot share it. He is very shy and very scared, and wants to return home.  He is kept in a makeshift cage, and is being held for ransom.

The combat encounters are going to be simple, just bandits of varying types. The empty rooms are similarly easy, they just need a little bit of flavor to make them stand out from simple empty rooms. Lets say we're designing this dungeon for 4 player characters, and since they're level 1, that gives us a budget of 8000 coins worth of treasure to spread around.

So lets say our finished rooms/encounters are as follows:

• A statue of a god with antlers and 4 arms. If one places something important to them onto the statue's lap, the item disappears and they become blessed with superhuman strength, along with growing some small antlers out of the top of their head.
• A small underground stream, that glows faintly. If one drinks from the stream, they either regain 1d6 health, or become violently ill, taking 1d3 damage and a -1 penalty to attack rolls for the rest of the day. Roll a d6 to determine which occurs (evens is 1d6 health, odds is violent illness).
• A chest with a poisoned latch (saving throw or take 2d6 damage). Contains a magical potion of healing (the drinker regains 1d6+1 HP), along with 1500 coins.
• A tripwire is hooked up to a crossbow, if a saving throw is not made when entering the room, one takes 1d6+1 damage from the bolt.
• A deerskin rug covers a hole in the floor, with spikes at the bottom (saving throw or take 2d6 damage). A gem worth 500 coins is at the bottom of the pit.
• A tripwire causes a large rock to fall on the head of any who activate it (saving throw or take 1d6+2 damage and be knocked unconscious).
• A tough old woman with an eye patch and a necklace with an eye pendant. She has a small chest containing 6000 coins in the corner. Her name is Barbara, she is the leader of the bandits, and will try to get the party to join her group. Her necklace can be used once per day to cause one person within line of sight to be paralyzed for 2d6 rounds, without a saving throw. 
• A mute boy dressed in expensive clothing is trapped in a makeshift wooden cage. He is crying silently, and wants to go home. He is being held for ransom by Barbara and her bandits.
• 4 bandits, armed with pistols (d6 damage) and daggers (d6-1 damage).
• 2 elite bandits, with great-axes (d6+2 damage). 
• 3 bandits, armed with short swords (d6 damage) and shields, along with a hound.
• 1 elite bandit with a blunderbuss (d6+2 damage), and 2 bandits with crossbows (d6+1 damage).
• A bandit armed with a longsword (d6+1 damage), with 3 hounds.
• An elite bandit with a battleaxe (d6+1 damage), a bandit armed with a dagger (d6-1 damage), and a hound.
• Flint arrowheads, arranged into the shapes of ancient runes.
• A statue of a bearded old man.
• A pentacle is carved into the floor.
• Carvings on the walls depict various deities frolicking and cavorting in the woods.
• Bones dangling from the ceiling.
• A skeleton with an arrow in its shoulder.

We also need to write combat statistics for any creature which may be harmed by the PCs (which unfortunately might include the mute boy).

Barbara

HD 4

AC light

ATK 2 pistols

DMG 1d6

HDE 4

Mute Boy

HD 1/2

AC unarmored

ATK 1 punch

DMG 1d3

HDE 1/2

Bandit

HD 1

AC light (may have shield)

ATK 1 weapon

DMG by weapon

HDE 1

Elite Bandit

HD 2

AC medium

ATK 1 weapon

DMG by weapon

HDE 2

Hound

HD 1

AC light

ATK 1 bite

DMG 1d6

HDE 1

Now that all that is done, all we need to do now is make a dungeon map and number the encounters, and our dungeon is complete!

For making a dungeon, I personally recommend either just doodling a flowchart on paper or using Dungeonographer, a dungeon mapping program with a free version.

I just did a simple flow-chart style dungeon using Dungeonographer, adding numbers in MSpaint.

Now, all I need to do is number the encounters and I'm done!

1. Flint arrowheads, arranged into the shapes of ancient runes.

2. A tripwire is hooked up to a crossbow, if a saving throw is not made when entering the room, one takes 1d6+1 damage from the bolt.

3. 3 bandits, armed with short swords (d6 damage) and shields, along with a hound.

4. A chest with a poisoned latch (saving throw or take 2d6 damage). Contains a magical potion of healing (the drinker regains 1d6+1 HP), along with 1500 coins.

5. A deerskin rug covers a hole in the floor, with spikes at the bottom (saving throw or take 2d6 damage). A gem worth 500 coins is at the bottom of the pit.

6. A statue of a god with antlers and 4 arms. If one places something important to them onto the statue's lap, the item disappears and they become blessed with superhuman strength, along with growing some small antlers out of the top of their head.

7. A tripwire causes a large rock to fall on the head of any who activate it (saving throw or take 1d6+2 damage and be knocked unconscious).

8. 2 elite bandits, with great-axes (d6+2 damage).

9. A statue of a bearded old man.

10. 4 bandits, armed with pistols (d6 damage) and daggers (d6-1 damage).

11. A small underground stream, that glows faintly. If one drinks from the stream, they either regain 1d6 health, or become violently ill, taking 1d3 damage and a -1 penalty to attack rolls for the rest of the day. Roll a d6 to determine which occurs (evens is 1d6 health, odds is violent illness).

12. Carvings on the walls depict various deities frolicking and cavorting in the woods.

13. A skeleton with an arrow in its shoulder.

14. A pentacle is carved into the floor.

15. A bandit armed with a longsword (d6+1 damage), with 3 hounds.

16. An elite bandit with a battleaxe (d6+1 damage), a bandit armed with a dagger (d6-1 damage), and a hound.

17. 1 elite bandit with a blunderbuss (d6+2 damage), and 2 bandits with crossbows (d6+1 damage).

18. Bones dangling from the ceiling.

19. A mute boy dressed in expensive clothing is trapped in a makeshift wooden cage. He is crying silently, and wants to go home. He is being held for ransom by Barbara and her bandits.

20. A tough old woman with an eye patch and a necklace with an eye pendant. She has a small chest containing 6000 coins in the corner. Her name is Barbara, she is the leader of the bandits, and will try to get the party to join her group. Her necklace can be used once per day to cause one person within line of sight to be paralyzed for 2d6 rounds, without a saving throw.