Monster Math [warning, math inside]

[Bjarkmundur]

After a couple of days of thinking about this, I've come to the conclusion that when building an encounter it is best to use the guidelines given in the DMG and MM regarding XP and CR, and use 1st party monsters.

I can't however stop to wonder how the developers learned what is a good challenge and what is not.

What is the math behind a monster's xp value, and how did the developers create the "adjusted xp value" system?

There most be some "hidden value" for each stat that help developers creating balanced monsters. At some point one developer must've said "I need stats for a 700xp monster", and then had some easy guidelines to follow to help him work it out.

I'm trying out my own math to create some monsters, and they seem to be way off target, no matter what I do.

[Bjarkmundur]

I'm trying out a simple system of guidelines.

Since 5e has bounded accuracy, it mostly comes down to HP and Damage Output.

I was thinking about this, and reached the conclusion that a encounter for four 3rd level PCs must have some guidelines in check so that it takes the monsters at least x turns to deal Y damage. This must have been done at some point, just so that it could be guaranteed that the PCs will be alive after the first round of combat.

And in turn, there most be some guidelines that say an encounter for four 3rd level character must have at least x HP, or it will simply be over in one turn.

I'm trying to figure these guidelines out, but nothing seems to make sense.

[Man_Over_Game]

After a couple of days of thinking about this, I've come to the conclusion that when building an encounter it is best to use the guidelines given in the DMG and MM regarding XP and CR, and use 1st party monsters.

I can't however stop to wonder how the developers learned what is a good challenge and what is not.

What is the math behind a monster's xp value, and how did the developers create the "adjusted xp value" system?

There most be some "hidden value" for each stat that help developers creating balanced monsters. At some point one developer must've said "I need stats for a 700xp monster", and then had some easy guidelines to follow to help him work it out.

I'm trying out my own math to create some monsters, and they seem to be way off target, no matter what I do.

There's a part you're missing, and I'd read up on it here: https://rpg.stackexchange.com/questions/69206/ogre-cr-calculation-is-it-wrong-or-am-i-missing-something

Basically, numbers aren't everything. Sometimes, you just gotta recognize that certain aspects of monsters makes them harder or easier based on the capabilities of your players and the world itself.

If you don't have silver or magic weapons, Werebeasts are going to tear your players to shreds regardless of their CR. If your characters are all 8th level casters, it doesn't matter how big your party is if you're against a Rakshasa.

In the example in that link, a poster asks why an Ogre is a CR 2 creature when it is calculated as a CR 1 level of experience when it comes to the numbers. The answer? An Ogre can kill a level 1 player in a single turn, so that bumped it up to CR 2 status (when it's actually a fun challenge to pit against players).

[Bjarkmundur]

Strictly average stats for a 1st Level character must be around 10HP, and around 1d8+3 damage.

So it stands to reason that an encounter designed for 4 PCs must have at least 4d8+12 worth of hit points, and less than 10DPR, divided between the monsters they are fighting.

Of course this gets more complicated with levels, which is why I keep using the word "guidelines".

[Man_Over_Game]

For more specific stuff, there's an entire section in the DMG that goes over creating a monster's statblock, all down to determining its "Defensive" and "Offensive" CR. It goes down to the itty-gritty details.

Someone actually reverse-engineered the internal spreadsheet they used to create monsters that they don't release to the public. The method we see in the DMG is basically WotC's version of simplifying and reverse-engineering the process to players (they didn't release the spreadsheet because, well, they want to continue selling Monster Manuals), but someone took it a step further and gave a better understanding. His blog and findings are here: http://blogofholding.com/?p=7338

[Bjarkmundur]

I've played dnd long enough to realise that with playtesting, everything changes.
Which is probably exactly what happened to your ogre.

There must've been some guidelines in place for the beta version, right. Something like "here's a bag of stats and features. Now, let's run 500 playtest and iron things out"

With each playtest, you get better and predicting the results, and thst will happen to me as well.

Hence, looking for guidelines, not miracles.

[Unoriginal]

You're missing the forest by looking for a garden.

The DMG already tells you how the designers determined what was a monster's CR. CR being in itself only a fraction of encounter design.

And XP is very much a secondary concern.

[PhoenixPhyre]

There are a few very simple considerations, but they're not nearly the whole story.

XP/CR fits a very nice quadratic equation: XP(CR) = 64.784 CR^2 - 79.321 CR + 221.28.

More importantly, if you take the adjusted XP/adventuring day guidelines and the XP thresholds, you find that there's a nice "4.5 full adventuring days per level" baseline throughout all of tier 2 (the main focus). Accounting for the difference between adjusted XP and awarded XP (but also including things like XP rewards for quests), you get somewhere between 4 and 5 full adventuring days (note--this is not the same as 4-5 in-game days) per level. You also find that if you do median encounters in each bracket (so halfway between a medium and a hard, for example), the following adventuring day (or permutations) will work at almost every level: Medium, medium, short rest, hard, short rest, medium, medium.

As for the underlying numbers (HP, DPR, etc), it tracks pretty well with the following assumptions:
1) A monster of CR X should be able to drop a "squishy" character to 0 in one round if everything hits and deals average damage.
2) Monsters should survive between 2 and 4 rounds of being focused by a party of 4.
3) Level-appropriate monsters should hit "tanky" PCs about 30% of the time and "squishy" characters about 65% of the time.
4) Level-appropriate monsters should be hit about 55-70% of the time by PCs.

But really, all of these are secondary. The variation in MM monsters is large. The average standard deviation in HP (averaged across all monsters of all CRs) is 25 (about 1.5 CR worth). The average standard deviation of DPR is 13.7 (more than 2 CR worth). The maximum standard deviation in DPR is 68.8, at CR 14. As a note on that last one, the average DPR of CR 14 creatures is only 128. So that's a huge variation.

Playtesting reveals all sorts of interesting things, and it may or may not be predictable. And the other factors in the encounter-building process are much larger than the pure numbers.

[Bjarkmundur]

Wait, there's an entire table in the DMG I didn't know about?.? :0

[Unoriginal]

...Did you read the Creating a Monster section of the DMG?

[Bjarkmundur]

.... Reading it now and apparently.


THERE'S AN ENTIRE CHAPTER IN THE DMG I DIDN'T KNOW ABOUT.


How come I've been wondering about monster creation for three days, and this wasn't the first reply to my questions xD

.... Well, live and learn.

Next time someone asks "I need help creating a monster", just answer "DMG p274"

[Unoriginal]

I assumed you had read it and weren't satisfied by it.

I suppose it is wrong to assume.


Also several people, me included, said they were using the DMG guidelines and you didn't react to it.

[J-H]

For more specific stuff, there's an entire section in the DMG that goes over creating a monster's statblock, all down to determining its "Defensive" and "Offensive" CR. It goes down to the itty-gritty details.

Someone actually reverse-engineered the internal spreadsheet they used to create monsters that they don't release to the public. The method we see in the DMG is basically WotC's version of simplifying and reverse-engineering the process to players (they didn't release the spreadsheet because, well, they want to continue selling Monster Manuals), but someone took it a step further and gave a better understanding. His blog and findings are here: http://blogofholding.com/?p=7338

Thank you! I have the PDF printed off from this link. So. Easy.

[Bjarkmundur]

For more specific stuff, there's an entire section in the DMG that goes over creating a monster's statblock, all down to determining its "Defensive" and "Offensive" CR. It goes down to the itty-gritty details.

Someone actually reverse-engineered the internal spreadsheet they used to create monsters that they don't release to the public. The method we see in the DMG is basically WotC's version of simplifying and reverse-engineering the process to players (they didn't release the spreadsheet because, well, they want to continue selling Monster Manuals), but someone took it a step further and gave a better understanding. His blog and findings are here: http://blogofholding.com/?p=7338

This is beautiful, thank you so much

[Unoriginal]

They did the math

They did the Monster Math

They did the math

It was a graveyard smash

[Bjarkmundur]

They did the math

They did the Monster Math

They did the math

It was a graveyard smash

Bwahaha xD