I must create a system, or be enslaved by another man's. I will not reason and compare: my business is to create.

- William Blake

Thursday, July 15, 2021

A (minimalist) d20 hexcrawl... and dungeoncrawl

I ran a couple of D&D 5e campaigns (Curse of Strahd, Tomb of Annihilation) which were basically hexcrawls (although neither were particularly good as hexcrawls).

One thing that bothered me was the amount of dice rolling I had to do whenever the players moved around. Scouting, getting lost, encounters, weather. etc. Also, there were no particular rules on how the encounter happens - what's the distance? Can one party hide from the other? etc.

I wanted to reduce the thing to one single roll (or, at least, fewer rolls).

Anyway, here is the minimalist d20 hexcrawl. Written for 5e D&D, Dark Fantasy Basic, or any other version if you adjust the numbers.


First, the chance of encounters is baked in the d20. So, if the chance is one in 5, an encounter happens if you roll 5, 10, 15 or 20. One in six, and it happens on 6, 12, 18. One is three, and it happens on a 3, 6, 9, 12, 15, or 18. And so on. Not perfect, but really close.

(Notice that, in some cases, you could add another layer here; for example, you could have 1-in-4 chances of encounters and 1-in-3 chances of bad weather; if you roll 12, you get both; but that will occasionally create strange results if you don't change the numbers a bit).

Now, roll you also use this d20 to make a Survival (or Perception etc.) check for whoever is leading the party. The DC is 15, or more for a place that is hard to navigate (desert, fog, thick woods, etc.).

Fail, and something bad happens (you get lost, surprised, delayed, trapped, exhausted, distracted, tracked, etc.). You can add some critical failures on margins of 5+ (or a natural 1; see below).

Succeed, and you're in the right path. If you get 20 or more, you also get a perk. 25+, two perks, and so on. Some examples:

- Perceive a foe before it can see you.
- Find food.
- Find valuables.
- Find a secret passage or shortcut.
- Move 50% faster.
- Etc.

If more than one perk would be appropriate, the PCs get to choose.

Let's take Curse of Strahd as an example. Start with a roll every couple of hours (test Perception the roads, Survival in the woods, Insight in the castle or temple). You have a 1-in-5 chance of encounters (1-in-4 at night or in the woods, 1-in-3 if both). Fail in the woods, you get lost or surprised. Fail in the roads an you get ambushed (if there is an encounter) or... nothing. Walking through a road should be easy if there is no encounter.

I'd probably make something nasty/awesome for natural 1 or 20. No matter how skilled you are, exploration will often be dangerous... or rewarding.

You could get lost inside Castle Ravenloft, for example ("Was this room here before"?), giving the whole thing a nightmarish twist. Or let Strahd appear on the road for some hit and run on a Natural 1, if appropriate. Or a giant goat, Roc, etc. (see Curse of Strahd).

Notice you can use the same reasoning for dungeons, mazes (use Insight), caves, etc. You can replace rolling for encounters, treasure, and surprise with a single roll.

Of course, if you want everybody to roll, they can roll with disadvantage, etc. Say, the party gets ambushed, but with a good roll some PCs can avoid surprise.


  1. Gonna have to give this a try; this is a nice elegant approach. Good stuff!

    1. Thanks, glad you like it! Let me know how it goes!