D&D 5E Encounter difficulty: how to fix it.

Gobelure · Oct 8, 2014

First, I would like to stress that I love the way 5E is going up to now. A lot of effort was put to provide a game that is both rich in possibilities and at the same time simple to run. Well done ! However, when it comes to encounter building, there is a huge level of complexity which gets added and it is almost impossible to handle it without a computer. Even if there are really usefull apps already available, I want to be able to run a game offline, just with pencil and paper. The game is easy to run, and encounter building should be as easy. Fortunately, after some thought I came with a simple way to implement this.

But first, an important disclaimer : already with previous versions, encounter balancing was more an art than a science. My impression is that with 5E it is even more true: depending on the PCs tactics and on the monster synergies, a single number representing the encounter challenge can at best be indicative. CR is not the ultimate truth, so please don't complain if on a given encounter for a given group you find it way too easy or too hard. That's just 5E life !

In the following, I will assume that the DMG Basic rules for encounter building are providing the best guess, and I only will tweak the math to achieve two goals. The first one is to make it simpler. The second is to cure the "3 rats and a lich" bug, which basically says that a CR21 lich in company of 3 rats is as tough as a CR24-25 monster. So, for pack of monsters of almost the same level, my system will retrieve the difficulty rating of official rules, where it will improve it for wildly different CR mix. Plus: you forget forever about encounter XP mutipliers.

The simple way to compute encounters challenge

Philosophy of the method is :
1. Forget XP for encounter building, only use power equivalent levels (or PELs)
2. Compare PELs for PCs and PELs for monsters and deduce the lethality of the enounter.

Player Characters PEL :
PC equivalent level is almost player level, with only a few exceptions. Use the table below

Player level	PEL
1	1
2	1.5
3	2.5
4	3
5	5
6	6
7	7
8	8
9	9
10	10
11	11
12	12
13	13
14	14
15	16
16	18
17	20
18	22
19	24
20	26

Monsters PEL :

Convert each individual monster CR to it's EL using the following table

Monster CR	PEL
0	1/3
1/8	2/3
1/4	1
1/2	1.5
1	2
2	4
3	6
4	8
5	11
6	13
7	15
8	18
9	21
10	24
11	28
12	32
13	36
14	40
15	44
16	48
17	52
18	56
19	60
20	64
21	76
22	88
23	104
24	120
25	136
26	152
27	168
28	184
29	200
30	216

Encounter challenge :

a. Sum up all PCs PELs get the Total Party Equivalent Levels (TPEL)
b. Sum up all monsters PELs to get the Total Monster Equivalent Levels (TMEL)

Encounter is easy(*) if TMEL ~ 40% to TPEL
Encounter is medium if TMEL ~ 60% to TPEL
Encounter is difficult if TMEL ~ 80% to TPEL
Encounter is deadly if TMEL ~ 100% to TPEL

(*) Assuming Easy is 25% of XP with respect to deadly… The table provided in the DMG preview has however an inconsistent definition of easy across levels. Not a big deal, you can just ignore it. What matters is to have a TML lower than the TPL. The lowest, the easiest.

Summary PDF

Dnddungeoneer made an awesome PDF out of these table. Check it out !
Player Level Charts.pdf

Example :

A CR21 lich and 3 rats is PEL 76 + (1/3)*3 = 77, so basically… a lich !

The math behind the scene :

This section is only meant for math-oriented people.
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What did I do here ?

First, I realized that the Encounter XP scales as the number of monsters to the power 3/2.
Indeed, XP for 4 monsters is 4 times the base XP, times 2 for 4 monsters. Total : 8 times the XP, which is 4^3/2. It also works approximatively for other numbers of monsters.

Second, I checked that the strength of a PC group scales with the number of PCs to the power 3/2.
If I have a deadly encounter opposing 4 PCs and 4 monsters, it means than the individual monster XP is half that of the PC deadly scale (4 times deadly scale divided by 8, see above).
Then, a deadly encounter for 2 PCs will be 2 such monsters. It seems just logical, but let's check : 2 monsters is twice individual monster XP, and the multiplier is 2 as I have only 2 PCs : total multiplier is x4, which makes the encounter deadly for 2 PCs. Hurrah, the system is consistent.
As PCs strengh with number scales as monster strength, it is fair to assume that the power of PCs scale as their number to the power 3/2.

At the same time, it means that the XP value for a PC is the half the deadly encounter XP !

Now, is is just a matter of rescaling: saying that A N^3/2 = B M^3/2, is equivalent to state that A^2/3 N = B^2/3 M. In other words : instead of taking some crazy math according to monster numbers relative to PCs numbers, just do simple addition, and precompute the corrected XP scale to make it fit.

The formula I used for my tables above is thus PEL = (XP/49)^(2/3), approximated up to 10% to get numbers easy to remember.
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Elric · Oct 8, 2014

Great analysis. The key is that in your new tables PC and monster power scales more slowly with CR/levels, so that you don't need the "fudge factor" of a multiplier. You don't explain that as directly as you could. Here's how I put it in another thread, feel free to use any of the wording.

Elric said:
It seems to me that PC and monster power doesn't scale as fast in general as the XP numbers alone would imply (e.g., a CR 5 Hill Giant worth 1,800 XP is not as deadly as 4 CR 2 Ogres worth 450 XP each). So large numbers of lower CR monsters would be too strong relative to what the XP total suggests.

The encounter XP multiplier (basic DM guide, p. 57) helps to address that design flaw. However, the XP multiplier is itself flawed (as an encounter with an Adult Red Dragon and 3 Kobolds demonstrates).

My take is that some monsters are particularly dangerous in groups (e.g., with their own kind, like Intellect Devourers, or with any melee combatant, like Hobgoblins). Those should have been handled with special guidelines in their stat blocks (CR varies based on group composition), and XP should have simply scaled more slowly as CR increased (with the corresponding decrease in the XP budget encounter guidelines), thus obviating the need for a multiplier.

Also, one unfortunate typo:

Encounter is easy if TMEL ~ 100% to TPEL

Should be "deadly."

ExploderWizard · Oct 8, 2014

I will look this over and perhaps give it a try. I like it because it doesn't assume a party of a given size OR that everyone in the party will be the same level.

DM Howard · Oct 8, 2014

Gobelure said:
Encounter is easy(*) if TMEL ~ 40% to TPEL
Encounter is medium if TMEL ~ 60% to TPEL
Encounter is difficult if TMEL ~ 80% to TPEL
Encounter is easy if TMEL ~ 100% to TPEL

(*) Assuming Easy is 25% of XP with respect to deadly… The table provided in the DMG preview has however an inconsistent definition of easy across levels. Not a big deal, you can just ignore it. What matters is to have a TML lower than the TPL. The lowest, the easiest.

I think I like this, however ~100% of TPEL means it would be very hard (right?) not easy?

Astrosicebear · Oct 8, 2014

Nice analysis.

I think your PEL for NPCs is way off(assuming NPC=PEL, if not ignore since we dont know true NPC equivalents). Even looking at some of the NPCs in the MM or supplements, they are not close to the same as your PEL. Heck, I think a 8th level caster is like a CR3.

Dont see how this is any easier or quicker than adding up the monster XP and referring to a chart?

Skyscraper · Oct 8, 2014

Interesting stuff.

Back in the old AD&D days, where monsters had a level scaling from I to X (in roman numbering, mind you!), there were no encounter building rules. You had to follow your gut feeling.

I plan on trying to do just that in a conscious effort to move away from a math-oriented approach. Use intuition. This will of course yield some easy fights and some tough fights. And some of those will be unexpectedly easy or difficult. I think this is desirable.

I think that CR and hit dice are valuable, albeit very general, indicators of a monster's difficulty level. This allows a DM to sieve through the list of monsters more quickly. But otherwise, back with good ol' DM intuition. This is what D&D is all about baby!

Boarstorm · Oct 8, 2014

View attachment Gobelure Encounter Building.pdf

I created a really quick and ugly one-page PDF of this stuff for people to print out and give it a try, if they're so inclined. Sorry for stepping on any toes, [MENTION=6780929]Gobelure[/MENTION].