Encounter difficultly simulator - any requests?



Howdy, my game has been delayed a week so I’m ploughing the pent up energy into resources. One of the things I haven’t been able to get really comfortable with is designing encounter difficulty. As a result I’ve lent into getting players to roll to determine the number of npcs that spawn or by dialing up and down the difficulty based on how the encounter (ultimately this is likely a good way to be a good GM). But I’m still left feeling I should have a better sense of what the party can and can’t take down mainly so I know how many miniatures to prepare :joy:

So, over investing in an over-engineered solution I’ve tried to code a script to simulate the dice rolls and show who could win if the same encounter was played 1000 times.

Here’s a video on YouTube of what it currently looks like:

What I’ve love to hear would be what kind of inputs would would be useful to have (I’m sure the answer will show things I’m not thinking about as a DM), I’ve currently set Target as 12, but what other numbers would be good to input here? Do all the loot bonuses need including or does the random results from d20s and d4/6/8 damage give enough of an indication.

I’d also love to know if this would be useful to you if I made a web interface… what do you think?


Edit: Aftyer watching it, I see that you did not take into consideration the attack bonus of the PCs and the monsters? Perhaps a feature to add, please? :smiley:

I’m totally in! Making something like this available would make a lot of D20 DMs happy!

Make it so! o7

Oh, and by the way, I don’t know if you’ve ever seen this: https://youtu.be/NPH17prodgM Perhaps this will inspire you?


Thanks @BlazingPolyhedron yeah, I totally missed that in the rush to a first version and was overly focussed on the difference between PC and NPC defence. That makes a lot of sense.

Really appreciate the feedback, and seeing that other video certainly gives some food for thought on how far the statistics can go.


You did amazing work! I’m excited about this program and I can’t wait to see what you make of it! Please share it when its done! :grin:


Hacking on a better interface for entering the players, something that has sensible defaults, but then gives room too tweak all the numbers.

Next step is to figure out a smart way to model the weapon/spell variety without getting SUPER complicated.


I admire your enthusiasm here! I’m not here to shut you down, but I would like to offer a slightly nuanced counterpoint.

Balance is a false god.

How often when you face a real-world challenge are you confident that said challenge is “balanced” against your ability to overcome it?

If you balance encounters for where the PCs are at, they’ll slowly learn a sense of “we can handle this”. That’s not bad but neither is it necessarily exciting.

PCs should be faced with situations that stretch them, challenge them, and which they cannot mathematically win. Computing probabilities on rolls reduces the game to a statistics exercise, in which case why bother playing? No analysis will ever handle the situation when the players say “I offer this group of orcs safe passage through this region to the area beyond” or “we run away!” Or anything in between.

Again, you do you and if this is the kind of game you and your players want to play then by all means ignore me! But if you want to explore the depths of player creativity to see what zany ideas players come up with, then “balancing” encounters may not be the most satisfying approach of encounter design.

Throw something at the party that they cannot beat with the equipment they have on hand. See what they do to use the environment to improve their chances. See how they think beyond their character sheet to turn the odds in their favor. See how they think differently about “winning” in these contexts.


No offense Skippy, I hate calling you out like that 'cause you’re usually super duper cool, but I think that this counterpoint is unnecessary because it discourage people to explore their interests and strengths in the context of their favorite DIY TRPG. I’m sorry again. I hope you understand.


You could change STR to To-Hit Mod. and ask of the user to simply enter the average value of the party? Same for the WPN into Average DMG Mod. Beside, those numbers are usually the same since players often invest in their best combat stats.

But if you want the user to enter the values of every single PC, then may I suggest that you take into consideration the number of milestone rewards that they have accumulated. Especially in the later version of the game they can retain some as abilities rather than loseable loot. Perhaps allow the GM to also enter a number for monster milestone? It would simply mean trait or feature for the monster. How many traits or features do these monsters have, for example.


Hey @skippy thanks for that. I have to say I totally agree making sure everything is balanced would be boring.

As a baby DM I still don’t have an intuitive understanding to know if I am starting the encounter with something the players could handle or not. I have 4 players with 1 heart (only on our fourth session), I can guess that 4 enemies with 1 heart is a fair fight, but I have no idea what the difference in difficulty change is for 3 enemies with 2 hearts. That can make designing the ‘feel’ of the encounter hard. Have I made a cake walk or an impossible shield wall? - no idea.

For me goal wasn’t to get to 50% chance to win, but more to add a sanity check to say to this encounter is hard, this one is a super easy, but let me play with big groups of lots of fodder or 1 big baddie. So the number of rounds taken was a useful thing.

Of course, a series of nat20s can level any foe and a nat1s can make you fall fowl of the softest mob.

Personally I’m a massive fan of the Spawner Workshop as way to help fill my blindspot.

I’m just trying to figure out if the first round of NPCs is impossible or easy as I try to get better at this. There’s also the meta goal of better understanding the rules as a side-effect of the process.

How do you approach this, always start super-hard to make it gritty, or start easy in every case and dial-up difficulty? I’m keen to learn.


@BlazingPolyhedron absolutely no offense taken! I, too, was trying not to diminish anyone. There’s more than one way to play our hobby! Talking about these differences helps us all find new ways to have fun, and to grow in our understanding of the games.


I dig it. And again, raw numbers is only a small part of any encounter. What is a mage casts “Doorway” underneath a group of foes, sending them tumbling out to somewhere far away? What about the Seeker spell which never misses? What about Wild Growth or the Slayer ability or the Defender ability?

In my games, 1 heart foes are common, but I also sprinkle in a number of 1-hit foes - they fall at the first hit (effectively one HP) and represent mooks and super low level threats. But in large numbers they can be a big threat.

Big bosses usually have 2-4 hearts, but also have multiple actions per turn and a few signature abilities. Some of them will have no rolls, and always hit. Many big bads will have a health recovery mechanism.

The point I’m trying to make here is that hearts-per-player is, in my experience, an inadequate calculation. I hear you about learning what’s too little and what’s too much, and again I admire your zeal for this approach.

Take a look at some of the designs in official Runehammer adventures. Last Flight of the Red Sword, Orvald’s Tower, Doomvault, Heckoon Carapace - these are all great scenarios to learn from - they are each hard in their own different ways and should help you get a feel for what levers you can pull to adjust encounters for your players.

Just some well-intentioned suggestions from a guy who doesn’t like to math his games much!


To more directly answer your question “how do you do this?”: I wing it. Sometimes I create an encounter that I expect to be hard - 4 or 5 monsters, each with 1 heart and a boss monster with some hard-hitting attacks. Sometimes I create what i expect to be a minor nuisance - 4-5 monsters with 1 hit each.

No plan survives an encounter with the players, so I’m rarely surprised when the players waltz through the hard encounter, nor when they struggle with the easy encounter. Dice are fickle, for both sides, and I just go with the flow.

If the party is struggling, I’ll ask questions to help them think more creatively about the situation. I’ll remind them that retreat is usually an option. I encourage teamwork, and get them to work collaboratively for bigger results. I remind them of their Hero Coins, and award more in the moment for great choices or situational role playing.

If the party succeeds easily, I usually leave it alone and let them enjoy the victory. They dont know what’s coming, and are usually nervous about their odds in any encounter - no need for me to tweak anything in that situation. Let them have a win and some stories to tell. There will be plenty of hard encounters later on!


I think this is the “heart” of the issue for me :wink:

Does this that just from DM experience? 4/5+boss=hard or there any unspoken thought process or method to arriving at that conclusion. Why did you think it’d be hard? I think that’s the itch I’m trying to scratch here.

Great tip on the resources, I’d looked at Red Sword, but I think I need to lean into the others to expand the breadth of reading there.


Superficially, this is roughly one enemy per PC. Such enemies get a small bonus to hit and to damage, so they’re loosely equivalent to a standard PC.

Such an encounter lets PCs pair up each against an enemy, or choose to focus attacks against a single enemy. Such encounters typically “feel” threatening to the players and usually take a couple rounds to play out. The party is not usually overwhelmed nor do they typically trounce the enemies quickly.

Add in a boss, with an extra heart and a special ability or two, and the above encounter becomes harder. Even if the Target Number remains the same, the PCs have another combatant in the mix, requiring them to choose how to spread their attacks and defenses. The boss threatens higher damage with more success. Should the party focus on the boss, or remove the lower-level threats first?

Things can get even more challenging for the players if the enemies are smart. If the enemies work in concert to eliminate their highest threat they can seriously impair a party. Or they can work to isolate the party from one another so that player synergies are negated. Or the enemies can heal their injured to keep the combat threat going longer.

My players don’t know the strength of a new combatant at the outset. They see “four bugs skittering across the floor toward you” and have no idea if these are 1 HP bugs or 10 HP bugs. They don’t know the capabilities until combat starts. Every combat is inherently threatening to the players because they’re facing the unknown. Once they’ve encountered something, they get a feel for what that thing is like. “Oh, great, more bugs. Don’t waste your spells - just step on them.” Or “oh no, acid bugs! Retreat!”

All this to say, again, that “balance” is not a thing I shoot for. I don’t calculate Challenge Ratings for party level, or try to ensure the PCs always face a (mostly) fair fight. I give them encounters that are interesting and challenging, and I trust them to figure out how to overcome.

Every party is different, though, so as GM you need to read the room and take notes on how your players respond. Give them clues as to when things are going to escalate (change the Target Number, or just narrate the mess of bones that litter the floor ahead). Reward clever play and encourage them to think beyond their character sheet. They’ll feel good about every victory, and will learn to adjust tactics to deal with new situations.