The Basics of Creating a Custom Adventure

Behind the Screen –  The Basics of Creating a Custom Adventure

Behind the Screen is an article series designed to give information to the Dungeon Masters/Game Master. So they can make an informed decision on what campaign they want to play next.

Today, I will be going over how to create a basic adventure. I will try to keep it a bit generic so that it can be applied to all game systems. After playing a while as a character, you see how the referee brings the adventure alive and you wonder if you can do that yourself or maybe you saw, read, or talked about something that seemed like fun to send your characters through. Either way, you want to create this adventure and this is some guidelines to help you.

For the examples in this article I will be using 5th Editon Dungeons and Dragons, but please modify where you see fit.

The ideaIdea

It all starts with something that interests us, whether it was a book we read or something we saw that was cool. We decide that we want to run our players through it. So we start with the idea then we gather our books up and our computers and start researching on how to make it happen

Example: Adventurers decided to stay at a tavern only to find that the local goblin population needs a new King and the way they decide this is that the first goblin to reach the roof of the tavern is the new King.

The first thing we do is a research because we need to know what it is going take to create this new adventure for our players. I search and see if there is existing content to support my idea. Since my example is basic, I can find the stats for the Goblins in the Monster Manual, and I can do some research based on other modules for tavern sizes and how they access the roof.

In other cases, I might spend a couple of hours seeing if there are any homebrew solutions for my idea or created modules or books related to it, then I would either bookmark the site or purchase the materials needed to create it. If there are no materials, then I start preparing the books and tools I need to create the monsters or scenario from scratch.

After spitballing a bit and doing the research, we can decide if the idea is doable. In the example’s case: Yes. Since it is doable I start gathering the materials I need.

For the example adventure, I know I am going to need the Player’s Handbook, Dungeon Master’s Guide, and Player’s Handbook.


This is where we take the material we have collected and started putting an organized structure for our idea into an adventure format.

Taking in the following in account :

1) Player Level needed to Complete

2) Monster Stats

3) Site Description

I start to organize my idea/adventure into an outline :

  1. Adventurers arrive at the tavern (early evening)
  2. Goblins arrive on the hill outside the tavern around just before dawn (since they have to complete their task before dawn)
  3. Goblins start their swarming into the tavern and up to the roof
  4. Adventurers and Tavern patrons react according to a perceive goblin attack
  5. Resolution of Goblin King, Goblin Tribe Wipe, or Goblin Tribe Retreats to try again the next night

I know at point 1, that I will need an outline of the tavern and since I want to make it multilevel I will need to draw a baseline map and make sure I have wall/ceiling/floor stats.

At Point 2, I know that I want to have the Tavern surrounded by Forest on 1 side and a big hill on the other, so I will need to make sure I have information ready for the PCs about the surrounding countryside. Also, this point gives a goal for the goblins so that it is not quite as random as it seems.

At Point 3, I envisioned that it was a mass swarm of goblins from this tribe, so I will need to see how many goblins a party of 4 adventurers can handle and make sure my waves of goblins are limited to that. I also want to make sure I have a finite amount of swarms, so a little research into Goblin Ecologies from 5th or a previous edition can give me an idea of this.

At Point 4, I know that there is going to be windows and doors leading into the tavern, so giving the PCs a chance to react before the pending mayhem I might give them a couple of rounds to prepare for the goblin “attack”. Or maybe some quick perception skill tests to see the goblin scouts or goblins footprints as they came in on point 1 to give them even more time.

At Point 5,  I know that the combat has ensued. I also know that 1 round of combat is about 6 seconds. So giving the time frame of about an hour before dawn gives the whole adventure about an hour of in-game would be about 600 rounds. Which is a long time in the campaign, so I might say that it is about 30 minutes before dawn giving it about 300 rounds, still a long time but I want to show what can happen in just 1/2 an hour.

With the outline in place, I can start looking at the monsters and see what is a good amount for my waves. If I was running a different kind of adventure, I might choose 1 big monster and leave clues that the PCs might find and draw out the adventure with suspense or I might set up the PCs to go search for something specific to defeat a monster.


CR (Challenge Rating) is calculated based on a group of 4 PCs at the level. So a CR 1 monster could easily be handled by 4 level 1 PCs. Keeping that in mind, I can devise a way that gives both the monster and the PCs a fighting chance. If I was wanting a bigger monster to say a CR 4 Monster, I would have the PCs find something that helps equalize the combat like a relic that weakens the monster or a weapon that instantly kills it.

Since monsters have stats just like PCs they can also be advanced. Meaning that can become bigger and meaner. If I had a party of level 12 PCs I might advance the goblins so that they would be more of a match or maybe I might put some sort of temporary penalty on the PCs.

In the example, I am using Goblins which are CR1/4 Neutral Evil Monsters, Page 166 in the Monster Manual for the stats. So I know that it will take 4 Goblins for a party 4 Level 1 PCs to be even. Looking back in the 3rd Edition Dungeons and Dragons I found that a tribe of goblins can be from 40 to 400 goblins. Since I just want the goblin adults, I will omit the sergeants, lieutenants, etc. 3rd Edition Monster Manual Page 107 for the organization stats.

After finding the information I need for a tribe I can see, that 40 goblins would be about 10 waves and 400 would be about 100 waves. Since I want the goblins to occur in a swarm, I am going to use the lesser number for my low-level PCs. Stating that only 4 at a time can get into the building if they have properly secured it. If I was playing with higher-level PCs I might use the 400 and adjust the amount accordingly.

Since I now have my main adversaries I can move onto plotting and drawing.

The Plot and Drawing

I want the PCs to have every advantage they can to win the fight since the game is about the experience and not about killing off PCs I am going to make sure there is plenty of tables in the tavern as well as other impediments for the goblins coming in. I am also going to draw up a level 12 ranger with a favored enemy of Gobliniods that will be the “Mysterious” stranger that may help if the PCs start to struggle.

Also, when I write this all up on paper I will make sure that the stairs up and the hatch to get to the roof can only support 1 or 2 goblins on it, keeping the numbers down even further for the PCs. Every 10 goblins down, the tribe will make an overall morale check DC 15 (-1 per 10 down) to see if they run away.

With all those preparations in place, I will start drawing up my tavern and creating my NPCs. Same with the adventure, I will be outlining what I need.

  • 1 Bartender/Tavern Owner (level 3 commoner)
  • 2d4 Patrons (not counting the mysterious stranger) (Level 1 commoners)
  • Mysterious Stranger asleep upstairs. (To be used in case of an emergency)
  • Walls of the tavern will be made of wood so I will need stats for those, as well as the floors and the ceiling.
  • Maybe 10x10x10 Main tavern room and each room upstairs is 5x5x10
  • Outlying forest and hilltop

Once I have that all created I will move on to the last portion. Also with the drawing up with the patrons and the bartender I can make the waves a bit longer. Since every 2 PCs shift the CR the PCs can handle by 1, Max would be CR 4 which would be 16 goblins per round in a wave.

The Last portion

This is the fleshing out stage. Once I have all the structure in place, I will start fleshing out a story for why the PCs are there. Giving them an adventure hook to jump on or maybe it will be just a place that they will stop at while they are on their way to somewhere else in the main campaign. Beware though, they might want to investigate this and it might make your main campaign a lot longer to get too if they go down the rabbit hole a little too far.

Summoning it all up

Once you get your idea structured and outlined, fleshing out is the easy part. That is where the DM/Referee can make flourishes as needed. Then you can surprise your PCs with an impromptu adventure in the main campaign that can alleviate some of the pressure that was building up. Or Maybe you just one to run a one-shot and that is good also.

I hope this article was helpful, please feel free to read any of my other articles. Remember this might have D&D Flavor to it but the base concepts can be used in any gaming system.

As always if you have questions, suggestions, or concerns leave a comment below.

-Archon Del Noche


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The Basics of Creating a Custom Adventure
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