Thread by @vorpaldicepress

We can argue back and forth all we want about whether CR in #dnd5e works but in the end it comes down to this:

Players and Monsters are asymmetrical

As such, there will never be a perfect metric of Encounter Balance. It'll always be horseshoes and hand grenades

So what to do?

As designers (of player options, monsters, adventures, etc.) we have a skeleton key:

Playtesting

Nothing will tell a better story than actually using the content as many times as possible and aggregating the results, turning dials, testing the results, and concluding.

As DMs its not so simple. The point of CR/Encounter Balancing tools is to be able to ad hoc playable material outside of what is published.

What we need is better guidance into what goes into CR and Encounter Balancing, so we can better see where we stand.

Encounter Balancing is a matter of:

1. How long does it take for a group of PCs to kill the creatures (this should ideally be 3 rounds)

2. How much 'drain' (hp, resources, etc.) the creatures inflict on the PCs before they die.

So, what factors go into 1?

Damage.

A level 5 Battle Master Fighter (featless) of average build (Dueling, Longsword + Shield) can deal 144 damage over 3 rounds. Not factoring hit rate, crit, advantage, etc. just Superiority Dice, Attacking, and Action Surge

So 1v1, a monster should have no more than 144 HP if it has 0 AC.

Of course they won't have 0 AC, so lets factor in hit rate. The Fighter has a +7 Hit Modifier (+4 STR +3 PB)

They hit an AC 15 creature 60% of the time.

Now, that 144 is max damage. It's 102 average. We're looking for a 3-round sweet spot, so 102 average * 60%, that creature should not have more than 61 HP

Drop the AC to 10, hit rate becomes 85%, HP can go up to 87.

AC 20, 35%, 36 HP

Give it BPS resist? Half that HP.

Hyper simplistic situation, but you get the theory.

What about #2? the 'drain'? In 5e, the system only cares about HP drain. Why? Because every class has different resources, there's no way to account for that.

Which is an important point I'll circle back to.

So a "Deadly" encounter is an encounter where the HP Drain is > than the player's HP.

A typical lv5 fighter with +3 con mod has 49 HP taking the 6+CON after level 1.

So a Deadly threat to a lv5 fighter deals ~16-17 total damage per round. As in, actually deals, so we've got to account for AC.

What's a decent AC for a lv5 fighter with Longsword and Shield? 18? Chainmail + Shield? Might be Splint.

So a creature with a +6 modifier (assuming +3 STR or DEX and +3 PB, might only be +2 but then the ASI could be +4 so lets say +6) hits AC 18 at 40%

Now our creature's attack needs to deal 41 *average* damage per round. That's a lot of damage!

It certainly looks like that creature will absolutely wreck that fighter. But their 18 AC will save them right? Well, only 60% of the time. Balance would be a lot easier if we didn't use dice to determine outcome 😁 but I digress.

(coincidentally, a Deadly trap to a 5th-level character deals 10d10 damage, 55 average. Interesting? 🤔)

Lets say we don't want this creature to be Deadly. We just want it to be Medium difficulty.

If deadly is 100% drain, Easy is probably 0-10%, Medium is maybe 40%?

So now our target damage against that Fighter is 40% of 49, about 20. So now we're looking for about 16-17 average damage per round (remember 40% hit rate)

That could still very easily kill the Fighter. But dice are gonna dice.

So lets take a quick second to recap.

The Deadly creature at AC 15 has 61 HP and 41 average damage per round.

The Medium creature at AC 15 has 61 HP and 16-17 damage per round.

But wait a second. The AC and HP didn't change. What gives?

In 5e, CR is made up of two other challenge ratings and averaged

Offensive CR: The damage the creature can deal over 3 rounds
Defensive CR: The creature's 'effective' HP

A creature with 61 HP and 15 AC has a DCR of 1.

A creature that deals 41 DPR has an OCR of 5 and a creature that deals 16 DPR has an OCR of 3.

The Deadly creature has a CR of 3, the Medium creature has a CR of 2. Not a huge difference, but it's the journey not the destination..

Lets say we didn't know any of this. Lets say we grabbed a random CR 3 creature out of a book.

What if that CR 3 came from having an OCR of 1, and a DCR of 5?

A DCR 5 creature might have 15 AC but 131-145 HP

That will take the Fighter 5 rounds to kill on average.

And an OCR of 1? That's ~8 avg DPR. That's piddlywinks to the Fighter. They can sit and tank that for SIX rounds without even going down.

That, my friends. That is where the problem lies in using CR for Encounter Balance.

So what do we do about it?

What's my actionable DM advice?

It's not that simple. The information we need in 5e is obfuscated by numerous factors.

First, we need more information in a creature statblock:

Damage p/ Round and Effective HP.

And you do these two things with them:

Take your party's total effective HP (more on this later) and take each creatures in an Encounter's DPR, and figure out how many rounds you can survive.

Total EHP of the Party is 200, Encounter's DPR is 50, you can survive 4 rounds. Pretty lethal.

Second, we need your party's DPR (what, you don't calculate your player's DPR and write it down? do that too, because you sure as hell can't do an "average character damage per round by level" table, or can you? More research needed.)

and... (next tweet cause characters)

... take the party DPR, take the Encounter's total effective HP, and figure out how many rounds it takes you to kill the encounter.

Spin the example table. Party DPR is 50, Encounter EHP is 200, 4 rounds. A bit long, but not bad.

So how do we balance an encounter with this?

Well we've actually gained something here: Combat Duration. A new 'axis' to encounter balancing.

We have Combat Duration (probably a scale of 1 to 4 rounds) and Combat Lethality (Easy, Medium, Hard, Deadly)

First we pick a duration: 3 rounds.

A DPR 50 party needs an encounter of EHP 150 to hit this duration.

Then we pick a lethality: Medium

An EHP 200 party needs an encounter of DPR between 17 and 33 to hit this lethality.

Did you follow me all this way? Nice!

Was it worth it? Because we're not done yet.

Now we have a balanced Medium difficulty 3-round encounter!

Is this a ton of work? Yeah, it is.

Is it reasonable to expect DMs to figure all this shit out? Not really, no.

5e makes a whole bunch of assumptions.

1. Combat is 3 rounds
2. Characters of similar levels deal similar enough damage
3. Monsters deal their optimal damage each turn
4. All combats start at full HP and resources
5. No magic items or contributions to DPR/EHP outside ASIs/Class

Because of these assumptions, we have the CR and Encounter Balancing system that we have.

Why do we have these assumptions? So we don't have to do all that work I just did.

Oh right, I didn't talk about Effective HP.

You can't just sum up a party's HP. That'd be too easy.

You also have to factor in AC and other forms of mitigation like Flying, Damage Resistances, etc.

How do you factor all that in? Well, that's another missing piece of the puzzle.

That stuff exists in CR calcs as modifiers, so it could exist for Players too.

But it doesn't 🤷

God this is a long story. How do I tl;dr this?

D&D makes a bunch of assumptions, which don't match actual play! (the common offender being magic items, but also things like highly tactical PC play, 'surprise rounds', and other play factors)

As a result of this mismatch, we have a system that appears not to work.

It does what it sets out to do, but it needs to evolve with the current state of play.

And uh.

Good luck with that everyone.

What am I going to do?

At the table: I'm going to throw some horseshoes at it, with a backup plan when things don't work out as expected.

As a writer: I'm going to rely on playtesting.

I gaffed here and the OCR of a 41 DPR creature is 6, but you probably wouldn't have noticed if I hadn't said anything anyways ;)

Did you read all the way to the bottom?

Here's a discount link for a free copy of my Warden class for D&D 5e, which is totally balanced I swear! 😁

The code will remain active until August 1, 2022

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