The other day, I promised to share the amazing new system that I had been testing and tweaking off and on for a while and had been using to build encounters and monsters for my Dungeons & Dragons 5th Edition. And then I didn’t actually give you the system. Instead, I spent 5,000 words pissing and moaning about the way I’d have built the system better if someone had asked me. Because I’m an a$&hole. But at least I didn’t make you wait too long until the payoff. In fact, I feel so bad for putting it off even a little bit that I’m going to skip the Long, Rambling Introduction™. That’s right, I’m launching right into the article.

Be Ye Warned

As I explained in the practically nonexistent Long, Rambling Introduction™, this article is going to show you the system I have been using to build custom monsters and encounters for my Dungeons & Dragons 5th Edition game. But before I launch into the system itself, I need to post a couple of warnings about this system. I promise I’ll be brief.

First, this is a system for people who actually see the merit in building balanced encounters instead of flinging whatever s$&% they want at their party and then telling the players it’s their own damned fault if they get killed because they should have run away. I would have thought that would be obvious, but after having to moderate more than a few comments to that effect, it became apparent that you can never be too obvious for some people. Look, if you think encounter balance is useless, that’s great. Go do whatever the f$&% you want. You don’t need my permission to do it. Just go run the game you want to. Good for you. But no one wants to hear from you on an article clearly intended for people who want to adopt a modicum of modern game design practice and see the value in it. So shut the hell up and go run your game you absolute mouth-breathing moronic turd with a keyboard.

With that out of my system…

Second, this system has a problem. See, it’s a very elegant and easy to use system that would make everyone’s life a lot easier if it was actually the system in the motherf$&%ing rules. But it isn’t. The system in the rules is utter s$&% and it’s based on stupid assumptions about statistical treadmills, precision balance, and that the only difference between one monster and many monsters can be summed up with an XP multiplier. Now, that s$&% all drives me crazy. I can feel it every time I build an encounter and I’m f$&%ing sick and tired of it. But I realize I’m crazy.

Anyway, the problem is that the monsters in the Monster Manual just don’t work with my system. Because they were made the stupid, official way. So, if you take a monster from the Monster Manual, you have to tweak its stats a little to make it work. Now, I find that pretty easy. I just cross out its AC, HP, Att/Save DC, and DMG and write in new ones. Because that’s about all you have to tweak to make them useable my way. But I understand that’s not for everyone. And, to be quite honest, these days, I stat up my own monsters. I just make custom monsters exclusively these days. Which isn’t nearly as much work as it seems. Most of them are actually just custom versions of the monsters that already exist.

But that’s the warning. If you really want to embrace this system, you’re going to need to start building a library of custom monsters. And I wonder if it wouldn’t be worth inviting people to contribute their own monsters and compiling them together somewhere and gradually building a bestiary of Angry monsters. Hell, if I had the money, I’d hire the trusted members of my inner circle and start throwing together an Angry bestiary.

Third and finally, there’s at least a 50% chance that in six months, this whole system is going to end up obsolete. See, there is one problem left in the combat engine that this system doesn’t address and that it really needs to. And I am already working on the fix for that. And if I do eventually find a group of victims to test THAT fix and I do get it tweaked and working well, I’m going to come up with Angry’s Custom Monster and Encounter Building System Version 2. Or whatever. I don’t know what version number will actually get released. After all, this that you’re reading right now is Version 1.67 or something because I’ve been testing and iterating it across several one-shots, campaigns, and tests – in some cases without even telling the players – to get the numbers where I want them.

And by the way, that’s something else for you commenters to keep in mind. If you have a comment that sounds like “this looks neat, but I have no idea how it will play…” the answer is “pretty well, thank you.” Because, once again, I actually DO playtest my material before I share it. And if I share something I haven’t playtested, I f$&%ing admit it.

Anyway, on to the show…

The Best Way to Build an Encounter

Fortunately, except for a remark or two about specific comments I had to moderate, I got all of the b$&%ing out of my system. That last article devolved into me describing everything I hated about encounter building in the previous article. So, let me just jump ahead to what encounter building SHOULD look like. How do I want to build an encounter?

The best encounters are encounters in which a group of heroes confronts a group of foes in roughly equal numbers. That’s the baseline. And if I weren’t stopping myself from complaining, I’d complain about the fact that the D&D designers apparently drank a little too much bleach between 4E and 5E and forgot that essential point. And the best encounters are encounters where the heroes and monsters are roughly equally matched in terms of power. Mostly.

After all, the statistical treadmill thing sucks. Sometimes, players need to feel disadvantaged. Sometimes, they need to feel advantaged. And those feelings need to tie directly into the advancement system. I already talked about that last time in my 5,000 b$&%-fest. I’m not going to repeat it.

Now, ideally, that would be built right into the system. It isn’t something you want to leave up the GM. Like, it’d be great if the designers had set the statistics so the players would alternate between hard levels, Goldilocks levels, and easy levels. XP levels I mean. That is to say, it would have been great if they said “okay, level 3 should feel challenging and level 4 should feel just right and level 5 should feel easy and so on…” and built that right into the stats. That way, GMs don’t need to account for it. The system just provides that wobbling sort of challenge where the players’ power levels are sometimes ahead of the monster power curve and sometimes behind it.

So all I’d have to do as a GM is look at my players’ XP level and build an encounter to that and the game’s challenge curve would hit that wobble instead of a linear treadmill.

To build the most basic encounter then, I’d just have to pick out one monster for each PC whose level matched the party’s average level. Four first-level PCs against four goblins. Four third level PCs against three orcs and their pet warg. Whatever.

That’d be great. Except for the problem that it’d be limited, it’d be boring, and it’d require a HUGE bestiary. It’d be limited because every monster could only be used at one specific level. It’d be boring because every fight would consist of one monster per PC. And it’d require a huge bestiary because you’d need a big roster of monsters at every level to provide plenty of options for encounter building fun.

Now, there is an easy way to counteract the boring part. Include ways to build encounters with more or fewer monsters. All you have to do is recognize the fact that different monsters are built differently and account for that. 4E kind of did this too with the solos, elites, and minions. But it was kind of messy. And 4E suffered from a massive precision problem.

But we can counteract the precision problem and the problem of limited monster utility and the problem of the huge bestiary and also account for the wobbling challenging very easily. We just have to say “look, the difference between a CR 3 monster and a CR 4 and a CR 5 monster is pretty small all things considered and, besides, we want to present players with monsters that are hard at some levels and easier at others.” In other words, we give each monster a level range at which it’s a good challenge. If the players are at the low end of that range, the encounter will be harder. If they are at the high end of that range, it’ll be easier.

And that brings us around to the ideal way of building monsters: every monster has a range of levels at which that monster should be used to build challenges and every monster has a certain group size. That is, every monster tends to appear with a certain number of friends. So, to make an encounter with a specific monster, all you have to do is make sure they fall in the right level range and make sure you give them the right number of friends. THAT is my dream system for building D&D encounters. And THAT’S what my system ultimately does. Now, let’s look at the nitty-gritty.

Challenge Wobble and Tiers of Play

First, let’s tackle the problem of wobbling challenge and the power levels of various monsters. Because this is a problem I’ve already solved in previous articles. Years ago, in fact. And it is the first idea in this whole system I started testing. Years ago. I started building encounters by tier of play rather than by level.

D&D has 20 levels of gameplay, right? And while 20th level characters and 20th level monsters are much, MUCH more powerful than 1st level characters and 1st level monsters, the difference between one level and the next is reasonably gradual. You can safely through a CR 12 monster against an AVERAGE 11th level party. And if it’s the only encounter of the day and the characters can spend all of their resources, a SKILLED 9th level party can usually take on a CR 12 monster.

The point is, instead of being precise about monster levels, you COULD just say that a CR 12 monster is just fine for anything from 10th level to 12th level. And if all the monsters in your Monster Manual were built to specific level ranges, you could say “okay, level 11 is a hard level because the players are actually fighting CR 12 monsters and level 13 is easier because the players are actually fighting CR 12 monsters.”

Now, that said, there are places where the power level of the game does jump a little bit. There are actually four places where the PC’s power level changes substantially. The first three occur at 5th, 11th, and 17th levels. Those are the levels at which all spellcasters get an extra die of damage for their cantrips and also those are ROUGHLY levels at which the damage output of non-spellcasters also jumps due to their class abilities. Those are the levels at which the monk’s martial arts attacks increase in damage, for example. And those are the levels at which the fighter gets extra attacks or additional action surge uses. Roguish sneak attack increases more frequently, but there are increases keyed to those three levels and the other increases occur evenly between them.

The fourth substantial change in the power level of PCs comes at 2nd level for some classes and 3rd level for other classes. Because at one of those two levels, every character class gets to make a big choice about their build. Paladins choose an oath, warlocks choose a pact, fighters choose a martial build, and so on. On top of that, 3rd level is about the point where the characters stop being so f$&%ing delicate that a stiff wind will force them to start making death saves.

So, we already have this idea that there are four tiers of play. The first one covers 1st and 2nd levels. It’s a starter tier. And lots of people even skip that tier. After that, though, there’s three tiers of six levels apiece. Now, six levels are a bit large for a tier of play. You wouldn’t put a 5th level party against an 11th level monster. But six is a nice number because we want this wobble between easy levels, medium levels, and hard levels, right? So, what if we split each of those three big tiers into two smaller tiers.

So, a tier of play consists of three levels, say 4th, 5th, and 6th level is the Adventurer tier. Monsters at that tier are built roughly to 5th level standards. 4th level parties will find Adventurer tier monsters challenging. But then they gain 5th level and the monsters feel like more of an even match. Then, they gain 6th level and they find themselves trouncing the monsters and feeling like a badass. And then they cross into the next tier and the 7th level heroes are finding the 8th level monsters a challenge again.

The big question then is how you align the tiers to those three big power jump levels. Obviously, 1st and 2nd levels have to be in their own tier. But after that, where do you want the power levels to fall in the tier structure. And here’s where I admit I was doing it wrong for a while before I did it right. Because I have been building encounters to this standard for YEARS.

Initially, I said to myself that the power jumps should coincide with switching to a new tier because that’s when the PCs end up in a new weight class. So, I had 1st level as its own tier. And did 2nd to 4th level as the next tier. 5th to 7th was next. Then 8th to 10th. And that’s wrong. Because I was ignoring what the players wanted. If you, as a player, suddenly see your damage output jump because your spells are more powerful and you can do extra attacks, what are you expecting to feel like at the next play session? You’re expecting to feel like a bada$&. You want to trash the monsters. You want to rip the game apart. You want to feel how much more powerful you’ve become.

So, 5th level, 11th level, and 17th level need to be the last level in their tier. They need to be easy levels. And that makes sense if you think about the ratcheting power level in terms of the players becoming overpowered and then the game rushing to catch up. When the players have a substantial jump in power, the game SHOULD get blindsided a bit and then race ahead of the players again. That’s precisely the wobble you want.

My games are now split into seven tiers of advancement. Apprentice (1st and 2nd level), Journeyman (3rd to 5th level), Adventurer (6th to 8th level), Veteran (9th to 11th level), Champion (12th to 14th level), Heroic (15th to 17th level), and Legendary (18th level and beyond). And, for a long time, I built all of my encounters as if the party was always at the middle level of their tier. At Journeyman Tier, I built all of my encounters as if I had a 4th level party regardless of the PC’s actual level. At Champion Tier, they always faced 13th level encounters. And man did that alone change the feel of the game immensely.

Angry’s Amazing Encounter and Monster Building System v0.5

If you’re not into tweaking monsters or building your own custom beasts, I’m going to advise you to at least do the tier thing. Divide your game into the seven tiers of advancement I listed: Apprentice (1st and 2nd level), Journeyman (3rd to 5th level), Adventurer (6th to 8th level), Veteran (9th to 11th level), Champion (12th to 14th level), Heroic (15th to 17th level), and Legendary (18th level and beyond). And then balance all of your encounters to the middle level of each tier.

But that wasn’t enough for me.

Encounter Slots and Monster Size

So, now we’re envisioning a Monster Manual in which every monster is built to a specific tier of play and each tier covers three levels of advancement. Great. That’s half the problem solved. But what about the other half. What about figuring out the appropriate number of beasts for a given party?

D&D has this pain-in-the-a$& system of figuring out the equivalent single monster CR for a group of some number of monsters of some lower CR based on totaling up the XP for all of the individual monsters, multiplying it by some kind of difficulty factor, and then comparing it to the XP of single monsters. And because of that, it requires these clumsy fractional CRs to account for monsters that are supposed to appear in large groups at low to middling levels of play. And there is no f$&%ing reason for any of that.

Now, I am going to skip a lot of my reasoning here because it’s pretty dull. It involves noticing a pattern in the Encounter Multipliers table on DMG 82 and also remembering how 4E handled things. I’m just going to skip ahead to the way I think things work best. The number of monsters should be ROUGHLY based on the number of PCs in the party. And the baseline assumption for an encounter should be that the number of monsters is ROUGHLY equal to the number of PCs. That’s where monsters like orcs and wolves fit in.

But some monsters tend to outnumber the PCs, right? Things like kobolds and goblins and cultists and thugs. They tend to outnumber the party by ROUGHLY two to one. Two monsters for every PC.

Then there’s monsters that swarm and overwhelm the party. They REALLY outnumber the party. Things like giant rats and monstrous spiders and zombies. Things that come in hordes. They appear in numbers of ROUGHLY three to one or four to one.

On the other end of the spectrum, you obviously have monsters that show up alone. The party has them outnumbered ROUGHLY four to one. Dragons, hydra, beholders, vampires, liches, all the big stuff. The setpiece encounters.

Finally, you also have monsters that tend to show up in slightly smaller numbers than the party. Most often, these are the sorts of creatures that show up with bodyguards or as bodyguards to other creatures. The witch and her ogre, the wizard and his golem, Ornstein and Smough, that kind of thing. They are usually outnumbered ROUGHLY two to one.

Do you see what’s happening here? There’s a sort of conversion factor between these monsters. So, if you classify each monster based on the size of the group they usually appear in, you can actually figure out the equivalences and replace some monsters with other monsters. That is to say, a monster that usually comes in Pairs can replace two monsters that usually come in a Group. And four monsters that usually show up in a Mob can replace one monster that usually comes in a Group.

Put another way, you assume every encounter has three to five “slots” for monsters. Normal monsters take up one slot. Bigger monsters take up two slots. Or four slots. Smaller monsters take up a half slot or a quarter slot. Beyond that, two monsters of the same tier of play and the same organizational size are interchangeable. Instead of building a fight with four orcs, I can build with two orcs and one ogre. Or three orcs and four goblin slaves.

And again, because we’re okay with being less precise, it doesn’t always have to be exact. It doesn’t have to be exact to the number of players: four heroes can fight three or four or five orcs. And it doesn’t have to be precise to the number of slots. Three wolves or four wolves or five wolves can replace one orc. Or whatever.

The idea of just slotting monsters into position in an encounter and using monsters of an appropriate tier makes it very easy to quickly build a variety of encounters. And if you then build some variety into the monsters, you can add even more variety. For example, if I am building a goblin a lair, I might have three different types of goblins: a skirmisher, a sharpshooter, and a leader. The leader goblin might even be the equivalent of two normal goblins. The goblins might also have an ogre slave. And they might have a bunch of giant rats they’ve trained. So, I could build encounters with three to five skirmishers and sharpshooters, I could replace two of them with the leader or the ogre, I could replace one of the goblins with four rats, I could make the leader a beastmaster and have him show up with eight rats, the leader and the ogre could pair off, and so on. It’s very easy to mix and match. And if I needed to build a random encounter, it’d be easy to slap one together.

Long story short: every monster has a Tier – a three-level smear across which it can be used to build encounters – and every monster has an Organization size – the number of friends it normally appears with. Every encounter has three to five slots for normal monsters. Paired monsters take up two slots. Solo monsters take up four slots. Gang monsters take up a half-slot each. Mob monsters take up a quarter-slot each.

Oh, by the way, my Organizations are Solos who show up alone, Pairs which show up with a friend, Groups which show up in equal numbers to the PCs, Gangs who outnumber the PCs two-to-one, and Mobs who outnumber the PCs four-to-one.

And man can I slap together encounters quickly using that system. Or I could if I had a f$&%ing Monster Manual arranged that way. Which brings me to…

Build-Your-Own-Beast

Now, I’ve talked about this system vaguely to a couple of GMing friends and I’ve gotten some weird objections to it. The biggest one is “what if I want two dragons to show up” or “what if I want a dragon to show up with a group of kobolds?” That response confuses me because D&D already has that problem. That is to say, there are encounter balance rules and CRs and things and it can’t always do everything you want. I mean, in D&D as written, I can’t have my 1st level party fight a swarm of giant rats for f$&%’s sake. Three giant rats are already a DEADLY encounter according to the DMG.

This is precisely why custom monster building rules are provided as a supplement to encounter building rules. The beholder in the Monster Manual is meant for 13th level PCs. If I want to make it a good fight for my 18th level PCs or my 7th level PCs, I’m going to have to build my own beholder. And the same is true for my system.

Moreover, if I want to use my brilliant system, I need to find a way to quickly measure the stats of the monsters in the book to determine what Tier and Organization they actually are. And to tweak the stats if I want them to be different. Or to build my own monster if I don’t have the one I need for the thing I want to do.

Now, fortunately, D&D gives me all of the information I need to figure out precisely how to convert monsters from their system to my system. I just have to do a lot of math. And I did do the math. And I’m not going to spell it out. Because after I did all the math, I came up with a better way that was more versatile and faster anyway. And I’m going to share it with you.

See, there’s really only four numbers that determine the CR of a monster: HP, AC, average damage per round over three rounds, and attack/save DC bonus. And I already talked about why that is in the last part. I’m not going to go into it again. The thing to understand is that all of the other stats are just eye candy. It doesn’t really matter what the monster’s Strength modifier actually is or what it’s Proficiency bonus actually is if it puts out the right amount of damage with the right attack modifier. It’s good if these things DO align so that players can use that information to come up with plans. For example, if the players can determine that a monster’s AC is coming from its high Dexterity, they also know that spells that call for Dexterity saving throws are less likely to succeed. S$&% like that. But you can pick the HP, AC, dmg, and attack/save DC and then back into those numbers with the stats as close as you can and then handwave any minor differences that no one will notice.

So, what if you just had a big old table that said: “if you want to build a Group monster at Journeyman Tier, give it an AC of 14, 36 HP, +5 to attack, and attacks that output an average of 13 damage over three rounds.” And then you could open the Monster Manual and say, “lizardfolk put out 10 damage per round with an attack bonus of +4, they have 22 hit points, and they have an AC of 15; that puts them in Apprentice tier and they should come in Pairs or Groups.” Or even, “lizardfolk would make good Apprentice Tier Group monsters, but I need to cut their damage down. If I just drop the multiattack, they’d be perfect for that.”

But then, you also want to allow for some variation. After all, your monsters are being balanced for three levels of play anyway, so they have a lot of wiggle room. On top of that, it’s nice to be able to build variation into your monsters. Especially if you like to do what I do and build different monsters for different roles in the same group. Like, if you want to have lizardfolk who are tanky and lizardfolk who are DPSy and so on.

What if you provided a rating for each stat. Like, a Poor, Average, and Good AC for an Adventurer Tier monster or a Poor, Average, and Good Avg. Damage Per Round for a Heroic Tier Monster that comes in Mobs? So, you could build a monster by saying “I want to build a tanky Adventurer Tier monster. So, Good AC, Good HP, Average Attack, Poor Damage.” And then you could just take the numbers off the table, build around that, and be done.

On top of that, what if you could also account – ROUGHLY – for the effect of certain traits and special attacks. For example, Pack Tactics is the equivalent of a Good stat. So maybe I’d better scale down some other stat if I want to give this beastie Pack Tactics.

Could you do all of that with one table? Is it possible?

The One Table that Does All of That

Here it is (click on the table to see the full-sized image):

That’s the master custom monster building table that fits into the encounter building system that I have been building my monsters and encounters with. And I didn’t just make it with math. I started with math and added some logic. And then I evened off some of the numbers to make them work out neatly. And then I tweaked the hell out of it by using it a lot and playing out fights and using it in one-shot games and campaign games. I’ll admit it hasn’t been tested extensively at the highest levels of play. But from 1st to about 12th level, after about eighteen months of off-and-on tinkering, tweaking, and secret testing, I’m pretty happy with it.

Now, I will add a few words at the very end of this article about certain aspects of the math, but I know that isn’t everyone’s cup of tea. I’m just going to explain how to use it. And to use it properly, you do have to have SOME understanding of the custom monster building stuff in the Dungeon Master’s Guide which I have previously explained in this article.

Let’s say you want to build a monster. First, you’ve got a concept for the monster. And from that concept, you decide what Tier of play it fits into and how the monster generally Organizes itself into combat groups. Then, you decide the monster’s strengths and weaknesses based on its role. Monsters have five basic stats: AC, HP, Attack, Save DC, and Damage. But Attack and Save DC overlap. They fill the same spot in the math.

Anyway, decide whether each of those stats is Good, Average, or Poor. Consider each Good stat to be worth 1 point. Each Poor stat is worth -1 points. And an average stat is worth 0 points. When it comes to Attack Bonus and Save DC, consider only the better of the two. So, if a monster has a Good Save DC and a Poor Attack Bonus, that’s worth +1 point.

The number of points lets you know ROUGHLY how dangerous the monster is compared to other monsters of its level. This isn’t an exact science and it doesn’t play a direct role in encounter building. It’s a design tool. It lets you know when to back off or add a little more power. I call it Threat. Medium Threat monsters are best and they have -1 to +1 points. High Threat monsters have between +2 to +3 points. Low Threat monsters have between -3 to -2 points. +4 point monsters tend to be tricky for AVERAGE players. And -4 monsters tend to be pretty insubstantial for AVERAGE players. So I don’t usually push that far.

The table will tell you your target for each stat based on the Tier, Organization, and Quality. Just make those happen. As close as you can. HP and damage can be tricky because you’re trying to hit an average number based on a specific die roll. Just do your best. If you’re off a few points, so be it. Or compensate with other traits. For example, if you’re trying to make a Journeyman Tier Gang monster and you can’t hit the 8 points of average damage, 6 is the best you can do, maybe bring another stat up to Good to compensate for dropping the damage from Average to Poor. Or just leave it alone.

You also need to consider traits. DMG 280 to 281 gives this long list of monster features and how they impact the stats that are used to calculate the CR. And, frankly, I find that unnecessary. Obviously, if a feature just increases a monster’s damage output or something, you take that into account when you compute the average damage. For other traits, if it seems like it’s going to have an impact on the monster’s effective HP, AC, Attacks, Save DC, or Damage, just assume it’s worth +1 Threat and adjust accordingly. For example, goblins have nimble escape. They can freely disengage, move, or hide every round. That means they can stay out of harm’s way more easily and they’ll occasionally get advantage on attacks. Overall, that means they effectively have more HP and they have better attack rolls some of the time. That definitely provides them at least +1 Threat. And you could make a case that it’s a +2 Threat because it affects them both offensively and defensively. But then, it’s not an exact science.

If your monster has a lot of resistances or it can fly at low Tiers of play, cut the HP in half, just like the DMG instructs you to do. Thus, if you make a Journeyman wererat that shows up in Pairs – because they can almost hold their own, but you want to have some room to give them swarms of rat buddies – and give it resistance to Bludgeoning, Piercing, and Slashing attacks from non-silver or non-magical weapons, give it 30 HP instead of the 60 HP it should have.

As for calculating average damage, follow the guidance in the DMG. If the damage varies, figure out how much damage it’d do over three rounds and then divide that by three. If there are area attacks, assume they hit two targets. If something does ongoing damage with a save, assume the target takes the ongoing damage once and then makes the save. If the creature is a melee creature with an aura of damage, assume two characters will take that damage every round. Honestly, that’s all just common sense s$&%.

Beyond all of that though, remember to build monsters to their Organization size. Group monsters need ways to work together. Solo monsters get no use out of synergies, but they need ways to stay dynamic, to hold their own, and to avoid getting stun-locked by staus afflictions at high levels. Mobs and Gangs are going to appear in large numbers. Don’t make them complicated. A single attack is good enough. And any traits they have should be passive and easy to account for. You don’t want your party rolling 16 different saving throws every round because your mobs do ongoing damage that a save can end.

And really, that’s it. These days, this is how I’m building custom content for my games. I build monsters to specific Tiers and Organizations and emphasize different roles with Good, Average, and Poor stats. And I build encounters assuming I have three to five slots of monsters and that Solo monsters fill four slots, Paired monsters fill two slots each, Group monsters fill one each, Gang monsters fill a half-slot each, and Mob monsters fill a quarter-slot each.

Of course, I could make things A LOT easier and get rid of eight f$&%ing columns on that table if I just fixed up the action economy. Which I’ll probably be talking about in June or something.

A “Quick” Note on the Math Behind the Table for Interested Numberphiles

I just want to take a minute to explain a particular little detail about the math on the table. Because there’s a non-obvious bit of adjustment happening behind the scenes. See, originally, I did this all the easy way. I recognized that monster HP increased by 15 per level and that monster damage increased by 6 per level and that I could just divide the total HP and damage output among the projected number of monsters. Easy, right?

And note that my numbers have been cleaned up a little to provide nice, clean tables. For example, the DMG says a CR 10 monster has between 206 and 220 hit points. I chose 210 as the sweet spot not because it was the average of those numbers, but because it was the number that provides a nice linear 15 point jump from one entry and the next. In every case – except ONE, I think – the HP in my table for solo monsters falls just to the left of the middle of the range suggested by the DMG. But I do like that it provided a nice clean table. Also, notice that rounding off to the nearest whole number does change some things with the mobs. The same is true of the damage column.

ANWAY…

Point is, if one CR 10 monster has 210 HP, then a pair of Veteran Tier monsters should have 105 HP each and a Group of four Veteran Tier monsters should have 52.5 HP each and so on, right? And likewise, each member of the Group should spit out 16.5 points of damage to equal the solos 66 damage output, right?

Only, it doesn’t work that way.

There are A LOT of factors that play into the difference between one monster and two and four and eight and sixteen – which are, by the way, the numbers I used for my basic calculations. And arguments can be made for upping the damage for monsters that come in smaller numbers or reducing it or increasing the hit points or decreasing the hit points and so on. And I spent months going through them all. I promise you.

Ultimately, the biggest factor, bar none, was the fact that when the party fights multiple monsters, they can reduce the number of attacks the monsters spit as they kill the monsters. So, all else being equal, if the party focusses all of their damage on one foe at a time, the four monsters will put out less than two thirds the damage than one equivalent monster will do as their number of attacks dwindle throughout a normal combat of four to six rounds. Of course, once monsters appear that outnumber the party, there’s a limit on how many monsters the party can kill each round, so there’s a lot of ways to even analyze that problem.

To counterbalance that, you need to give monsters that appear in larger numbers more damage output. But if you push the damage output up too much, the really big groups of monsters will utterly destroy a party in the first round or two before their numbers start getting reduced. I think I realized I’d need something like 8 times the damage for a mob to spit out the equivalent of a solo’s damage throughout a six-round fight based on the assumptions I was using. And that would have been a disaster.

So, to keep from having to increase the overall damage output of the biggest groups of monsters to dangerous points – and I still gotta admit that Mobs are very dangerous at Apprentice Tier – I also increased the staying power of the monsters so they had more time to do more damage without spiking the damage in the first round.

I juggled these numbers a lot. And there was no way to really nail it perfectly. But I did hit a point where it felt good. Except at Apprentice Tier, but that’s a bug of the game system. Ultimately, what you’ll find is that, as the number of monsters increases, the total damage output of all of the monsters reaches about 200% of the damage output of an equivalent solo monster and the total hit points of all the monsters reaches about 150% of the hit points of an equivalent solo monster. And that got me to a very comfortable spot.

In the end, if mobs are dealt with well – using area effects and crowd control – they are easier than they should be, but if they aren’t dealt with well, they become pretty dangerous pretty quickly. Most importantly though: with this current iteration of the numbers, the fights definitely have a different feel to them.