Surf gets side-tracked for a while... But that's a good thing!

Part 3: Construction: CR & Size

OK I want to open this article with a couple of apologies.

First up, some folks felt that 'two introductions' for this series was excessive. I can understand this and I'd normally agree - be assured that I agonised over this when I was writing Before Building. But in the end I decided that a process-oriented build really does demand that the conceptual pre-work be done. It is far, far more important for this kind of build than for a result-oriented build. To those who felt put-out I do apologise and can assure you that it is not how I prefer to write a series of articles, so you shouldn't expect a repeat any time soon.

Secondly, I apologise for the lateness of this article. I originally indicated I'd post it almost a week ago, but as I started writing Part 3 I realised how fundamental CR is to the process. I was faced with a choice - do some quick and dirty analysis to work around it or do some solid analysis. So I chose the latter and disappeared down a rabbit hole for a while.

I think most readers will be happy that I did... I certainly hope so!

Let's have a look at the two foundational components of a D&D 5e monster - CR and Size. Then we'll use these to fill out some peices of an example monster.

Challenge Rating

So I had committed to leaving Challenge Rating (aka 'CR') analysis until the Monster Manual hit the shelves, but as I dug into 5e monsters I developed a deeper appreciation of something I had previously suspected. While CR clearly is a measure of how appropriate a given creature is for a same-level party to fight, it is also a foundational element in building 5e monsters. When we decide to build an opponent for the PCs, regardless of the approach we use, we have an idea of how challenging it should be. We may or may not have formalised it, but we do have an idea. I starting thinking of this as Target CR in order to differentiate it from the actual final CR.

I came to this realisation as I was doing some analysis to work around using CR when building monsters. Ultimately this lead me to analyze PC data earlier than anticipated. Interested readers might check out this thread on the wizards.com forums where I posted the data I crunched about Classes.

Several key components of monsters are based directly on Target CR...

This Handbook from Wizards Community Forums was posted October 2014 has since been deleted. There were a lot of great optimization guides and handbooks that were also lost when all the information on the forums was deleted. Fortunately, I pulled the original post before it was deleted, cleaned it up and did a lot of editing. I found this Guide on Conjuration to be particularly useful in play. Enter expected CR of the creature. Fill in the HP, AC, and other defensive attributes of the creature. Fill in offensives attributes of the creature. DPR is averaged over three rounds! Add any special Monster Features of creature. Be sure to read the Dungeon Master's Guide section on monster creation, pages 273 through 283. You can click on the.

D&D 5e HP Calculator. Class and Level: Constitution Modifier: Tough Feat Hill Dwarf Draconic Sorcerer. Hit Points Using Average Result: 8. Character Level 1. Second Class: 1. Third Class: 122 + Multiclass. Second Class and Level: Draconic Sorcerer.

A monster's Hitpoints are the result of it's number of Hit Dice, it's size and it's Ability Score modifiers. But how many hitpoints should my monster have? Target CR yields a Target HP range towards which we can build.

Dnd 5e Dmg

Monster Damage output results from a creature's traits and actions. A combat-focussed creature's damage is influenced by it's Ability Score modifiers, it's size, the weapon it uses, the number of attacks it makes and several other factors. A creature that focusses on casting spells mainly produces damage according to it's caster level. Creatures with other approaches produce their damage output via other methods. But what should this damage output be? Target CR gives us an appropriate range for this.

Proficiency for monsters is indexed directly off the creature's CR. We can simply use the Character Advancement table on page 10 of the Basic D&D v0.1 and use CR instead of level.

Ability Scores also appear to scale based on CR. We'll look at this more closely in Part 4: Construction: Abilities & HP.

Experience Points seem to be tightly bound to CR. While there are a number of gaps the XP rewards for the monsters presented in the Starter Set make it quite easy to fill in these gaps up to level 10 with a reasonable level of confidence. We can estimate values for the missing CRs using the following moderate polynomial:
XP = -0.3553xCR^3 + 60.485xCR^2 + 5.5534xCR + 155.52

Initiative Tracker; Power Attack Calculator; Random Generator; d20 Demographics Calculator. D&D3.5 Monsters to 5e On The Fly Introduction. This comes from jamesmanhattan on the EnWorld D&D5e forums. So this isn’t perfect, but it should get you very close to being able to use any Pathfinder or 3.5 monsters in D&D 5e. It should even allow you to run a 3.5 or Pathfinder adventure on the fly, including NPC’s.

It's important to note that our limited sample size makes it difficult to be confident of certain numbers past a reasonable level or CR. In this case we can have a high level of confidence that we are in the right ballpark with these XP numbers. Some of them might be a hundred XP or so out but they'll be pretty close and more than good enough for most uses. We'll revisit these as soon as there's more data, but it's what we have to use for now.

Note that I won't provide tables out past CR10 until we have at least some examples of creatures at these higher levels to analyze.

Prediction: I believe we'll see creatures up to at least CR25 in the Monster Manual, probably out to CR30 and maybe even beyond.

Size

Monster Size partners with Target CR to provide targets for most of the building blocks of a 5e monster, either directly or indirectly.

Size has a direct bearing on Hit Points (via Hit Dice), weapon damage dice and on speed. It may also influence other aspects of monsters.

Page 71 of the Basic D&D v0.1 PDF outlines the appropriate size categories in D&D 5e and Appendix B of the Starter Set shows us the HD size for most of these. Appendix B doesn't tell us the HD size for Huge or Gargantuan creatures, but it's pretty reasonable to assume that these are simply the next dice sizes up from Large.

Speed is normally thought of as an aspect of race - it's listed in the Racial Traits section of the Basic D&D v0.1 PDF, for example. I believe that this is primarily because Size is a component of Race. Note that Speed is not a 'hard' aspect of size, rather it is a starting point that can be modified and tuned to suit the specific creature you are building. Variance up to one size category above or below seems to be quite normal.

Prediction: Because of the relationship between Size and Hit Points I believe monsters of the smaller sizes will become less frequent as CR increases and that creatures past say CR10 will be predominantly Medium or bigger. We'll need the volume of data expected in the Monster Manual to confirm this.

Example: Human Pyromancer

Since this part of my blog focuses on the build-oriented approach to D&D 5e monster creation I thought it would be appropriate to provide some example monsters for illustration purposes. In these examples we'll normally omit parts of the stat block which we have not yet dealt with.

The idea behind the Human Pyromancer is a 'Glass Cannon' ranged attacker with an aracane fire theme. The intent is for this monster to blast the PCs from a distance, while receiving protection from melee type monsters and cover. Once the PCs get up close it should be all over for this guy. With some lower level meat-shield support it could be the central piece of a toughish level 5 or 6 encounter. It should have some longevity out to level 10 or so as lower-end ranged support for higher-CR melee creatures.

From a monster design perspective it will allow us to explore how spellcasting monsters are built in D&D 5e and thus also explore the math associated with casters. It will also allow us to illustrate the flexibility the CR guidelines for HP and Damage support.

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by Mike Shea on 12 September 2016

Note: This article is a rewrite of the original from March 2015.

For an even simpler approach to determine potentially deadly combat encounters, see The Lazy Encounter Benchmark, a Simple Benchmark for D&D Encounter Deadliness.

The D&D sourcebook Xanathar's Guide to Everything now includes an excellent alternative method for encounter building in addition to the encounter building rules in the Dungeon Master's Guide. Consider the guidelines below as another alternative for fast and simple encounter building.

You can also read another take on this topic at A New Dungeon Master's Guide For Building Encounters and download the Encounter Building Guidelines PDF from the Lazy DM's Workbook.

If you find this article useful, please check out Return of the Lazy Dungeon Master and the Lazy DM's Workbook for more tips on preparing and running your D&D games.

D&d 5e Point Calculator

The following guidelines aim to help Dungeons & Dragons dungeon masters quickly gauge the difficulty of combat encounters. These guidelines, like the encounter building rules in the Dungeon Master's Guide and the challenge rating of monsters in the Monster Manual, are not perfect. Instead, they are loose guidelines to help you quickly gauge the potental deadliness of an encounter that fits the story taking place at the table.

Quick Encounter Building Summary

Here's a quick summary of my proposed encounter building guidelines.

First, select the number and type of monsters that fit the story and the situation. Often, this is all you need to do.

Second, if you think such an encounter might be deadly for your characters, use the following guidelines to compare a monster's challenge rating to a number of characters at a particular level. If the encounter you designed goes beyond these guidelines either in the number of monsters or their challenge rating, its potentially deadly.

For 1st Level Characters

• One CR 1/4 monster per character.
• One CR 1/2 monster per two characters.
• One CR 1 monster per four characters.

For 2nd to 4th Level Characters

• Two monsters per character of a CR one tenth of the character's level.
• One monster per character of a CR one fourth of the character's level.
• One monster per two characters of a CR one half of the character's level.
• One monster per four characters of a CR equal to the character's level.

For 5th to 20th Level Characters

• Four monsters per character of a CR one tenth of the character's level.
• Two monsters per character of a CR one fourth of the character's level.
• One monster per character of a CR one half of the character's level.
• One monster per two characters of a CR three fourths of the character's level.
• One monster per four characters of a CR equal to the character's level plus 3.

Third, if needed, adjust the difficulty of the encounter by adding or removing monsters, increasing or decreasing the monsters' hit points, or increasing or decreasing monsters' damage.

A Deeper Dive Into the Encounter Building

The following is a more detailed look at the guidelines above. We focus on 'hard' encounters so we can understand when we might be potentially putting the characters in a deadly fight if the story leads to an encounter outside of the guidelines above. If an encounter is below those guidelines, we need not worry about it. The characters will likely defeat it and live to fight another day.

Thus, we need only use these guidelines when an encounter is potentially deadly so we can either scale it back or be prepared to fail forward should the characters get defeated.

Choose monsters based on the story. What monsters make sense for the current situation and direction of this story? You might know this ahead of time or might want to improvise a quick encounter right at the table. When designing an encounter, start with the story first and the mechanics second. When in doubt, read the Monster Manual to get ideas foor which monsters makes sense for the monster. Use the monsters by challenge rating index or the excellent Monsters by Environment list in appendix B of the Dungeon Master's Guide to help you pick the right monsters for the situation.

If needed, determine if the encounter is deadly. If we think an encounter might be deadly, we can use the guidelines above to see if that is in fact the case.

If the guidelines are too confusing, try using the following table. It has a more accurate comparison of a monster's challenge rating to a characters level. Note that this table follows the encounter guidance in the Dungeon Master's Guide. You can download this table along with the quick-use guidelines in this Encounter Building Guidelines PDF from the Lazy DM's Workbook.

Adjust the number of monsters, their hit points, and their damage as needed. These guidelines are loose at best. Encounters can be easy or hard depending on a lot of factors such as character synergy, player experience, magic items, environment, and many others. During the battle we can adjust the difficulty on the fly by increasing or decreasing the number of monsters as some flee or new monsters show up, increasing or decreasing hit points within the monsters' hit dice range, or increasing or decreasing the monsters' damage by adding or removing dice to their damage or increasing or decresing their static damage.

Mix and Match Monster Types

The guidelines above let you mix and match monsters of different challenge ratings in a single battle. For example, if you have a group of five level 7 characters, you can build an encounter with one challenge 5 troll (the equivalant of two level 7 characters), two challenge 2 ogres (the equivalant of two additional level 7 characters) and two challenge 1 bugbears (the equivalant of the one remaining level 7 character).

The math isn't perfect. Theoretically you could have five ogres and a troll instead of two ogres, a troll, and two bugbears. That's certainly a harder battle but it still falls within the guidelines.

Loose Guidelines for an Imperfect System

The challenge of any encounter in Dungeons & Dragons cannot be easily measured or quantified. The above system and that within the Dungeon Master's Guide doesn't guarentee a predictable outcome. There are too many variables to know how any battle is really going to go. Some of these include variance between monsters at the same challenge rating, the class mixture of characters, the particular spells a character group has access to, who wins initiative, circumstantial or environmental considerations, and the skills and proficiency of the players. Whether a group is fully rested or worn down will have a huge effect on how easily they can overcome the next battle.

Thus, all systems to determine the difficulty of an encounter in 5e will lack precision.

Due to the complexity of the encounter building rules in the Dungeon Master's Guide and the lack of precision in any encounter building system, we aim for the guidelines above that gives dungeon masters loose guidelines to balance encounters while acknowledging that the actual difficulty will still vary.

On the Action Economy

There's a good reason the Dungeon Master's Guide has two tables we must cross reference to put together an encounter. Regardless of the individual power of a monster, the difficulty goes up every time we add another combatant to the battle field. Regardless of how hard they swing a sword, two knights get twice as many actions as one.

We call this the action economy. The more total actions on one side of a battle, the stronger that side is. The multiplier in the standard encounter building guidelines in the DMG intends to account for this. If there are three to six monsters, they are significantly more effective than if there is only one. Thus we have a 2x multiplier on their experience point budget when we include them into an encounter. This increase in the action economy is why the rules for encounter building are so complicated. As Benjamin Reinheart often points out, the overall threat in combat increases at a geometric rate as you add more combatants to a fight.

For this reason, you likely want to have no fewer than one monster for the first four characters plus one additional monster for each character above four. Even an ancient red dragon is going to have trouble handling six high level characters and all of the things they can do in a round.

Not All Encounters Need Be Balanced

Dnd Cr Calculator 5e

The intent of these guidelines isn't to ensure that every encounter our characters face is 'balanced'. There should be many times our characters face small groups of easily defeated monsters and a few occasions where they might run into a foe they simply cannot defeat with straight-on combat. Instead, these guidelines are intended to help us understand if a battle might be unexpectedly deadly. If we're way above the baseline, we know things are going to be rough and can help our players see that. If we're going way below, we know it will probably be an easy fight. Varying difficulty is a good way to ensure the story and the game feel fresh.

Modifying the Guidelines for Individual Groups

As we begin to understand our group's actual power, we can alter these guidelines or throw them out completely. If a group of experienced players is running a strong group of well-coordinated and well-built characters, we can increase the number and challenge rating of monsters they face when the story calls for a big challenge. If things are still too easy we can increase the hit points of these monsters, increase the damage they deal, or both.

We can also go in the opposite direction with groups who aren't as experienced or well-coordinated. Fewer monsters, monsters of a lower challenge rating, or both will make battles easier for less optimized groups of players.

Again, these are loose guidelines meant to give us a starting point. As DMs, we are free to tweak these guidelines or throw them out depending on our goals and the actual results we see at the table.

A Simple and Powerful Tool for Easy Game Preparation

I wrote these encounter building guidelines to make your life easier when putting together a battle. Keep the numbers above in your head so you can quickly build a roughly balanced encounter for a challenging fight. Tweak these guidelines to suityour game and match the skills of your players and the power of your characters. Focus your attention on the grand story of the game you share together.

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