D&D 5e Monsters: Part 3: Construction: CR & Size

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...

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.

CR	XP
0	10
1/8	25
1/4	50
1/2	100
1	200
2	450
3	700
4	1100
✝5	1700
✝6	2300
✝7	3000
8	3900
✝9	4800
✝10	5900
✝ Not in the Starter Set

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

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.

Size	HD	Speed
Tiny	d4	10'
Small	d6	20'
Medium	d8	30'
Large	d10	40'
✝Huge	d12	50'
✝Gargantuan	d20	60'
✝ Not in the Starter Set

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.

Human Pyromancer

Medium humanoid (human), any alignment

Speed: 30ft

Challenge 5 (1,700 XP)

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.

 

Part 2: Construction: Before Building

Master Index

Part 4: Construction: Abilities & HP

D&D 5e Monsters: Part 2: Construction: Before Building

Surf talks about the preparations we need to make before building out a D&D 5e monster...

 

Part 2: Construction: Before Building

So what do we need before we start building a D&D 5e monster?

Well some way of recording the result, of course. And some way of doing some rudimentary calculations. The average laptop, tablet or smartphone should suffice. Or good old pen and paper.

But that's not really the point of this post. What we really need is the idea for the monster. That might seem obvious to most folk reading this, but with a process-oriented build methodology this is a pretty important thing!

You need a clear idea of the critter you are going to build!

Some might consider this some sort of "generic before-you-build-monsters advice", but this clear image does have a direct impact on monster creation. True, a certain amount of this mental image might be considered "fluff". But a good deal of it is directly relevant to the build process itself.

If you have a good idea for a monster this shouldn't take much time or effort to work out.

Following are the areas I generally try to have a handle on and the kinds of questions I try to consider.

 

Physical Aspects

This is all about the creature's physical appearance and physical presence (or lack thereof!).

Key questions to consider...

• How big is the creature in relation to an average adult human?
• What does the creature look like?
• How capable is it, physically?
• What else about it's physical form is unusual? Whether above or below average. Or simply unusual.

 

Modus Operandi

This area is all about how the creature gets along in the world.

Key questions to consider...

• Is it a melee type? Ranged? A caster? Something else?
• How does it attack?
• How does it defend itself?
• What are it's mental/spiritual/supernatural capabilities?
• What kind of persona does it have?
• How does it relate to other creatures?

 

Nature And Nurture

These aspects of a creature influence all kinds of things, from how creatures behave to skills to their attacks and more.

Key questions to consider...

• What is the creature's natural environment?
• What's the racial heritage?
• How do the creature's instincts tell it to behave?
• What was the creature's upbringing?

 

These questions aren't relevant all of the time. But considering these areas and thinking along these lines help us get a solid mental picture of the creature. And that becomes useful as soon as we start building the mechanics.

 

Part 1: Starter Set Monsters

Master Index

Part 3: Construction: The Core Choices

D&D 5e Monsters: Part 1: Starter Set Monsters

In which Surf shares some observations on monsters in the D&D 5e Starter Set and tells us what we can expect in upcoming articles...

 

Starter Set Monsters

First up no, this is not another Starter Set unboxing. This is not another "I just got the Starter Set" post. I was lucky enough to gain access to the Starter Set monsters about a week early and commenced my analysis then. I have yet to open my own personal copy of the Starter Set... It's waiting for me to finish writing this post!

 

First Impressions

The D&D 5e Starter Set contains the adventure Lost Mine Of Phandelver, which in turn includes the ten page Appendix B: Monsters. The first two pages of Appendix B discuss monster statistics and the remaining eight pages contain 27 monsters.

Now my goal with monster analysis has always been to peel back the covers on the underlying math, allowing us to construct reliable and appropriate Monsters. As you might imagine I wasn't expecting to be able to unlock much about 5e monsters with a sample size of a mere 27 low-level creatures! I was resigned to waiting for the Monster Manual release on the 3rd of October before I could do any useful analysis.

But I was to receive a very pleasant surprise!

 

The Good

It's apparent that after the last playtest packet Wizards Of The Coast wiped the slate clean and started fresh with both monster math and monster construction. It's readily evident that the monsters in the Starter Set support a straightforward method of monster construction. A few hours of preliminary analysis confirmed that the creatures all follow a consistent set of rules that facilitate a straightforward, process-oriented build method. On the few occasions where a creatures falls outside these rules the exception is for obvious reasons. Reasons that apply uniformly across other similar examples. This build process has some similarities to the way PCs are built, but is somewhat simpler and and looser.

Another benefit of following a process-oriented build is that it encourages the DM to think about the monster they are constructing as something more than raw numbers. It also promotes variety in the pool of creatures that emerge over time.

My instincts tell me that there is likely more than one way that D&D 5e monsters can be built. In fact, I get the feeling that if a result-oriented method isn't directly supported one can be built without too much difficulty... Given a sufficient volume of monster samples to draw on.

 

The Bad

The biggest issue facing analysis is the tiny sample size. Although a lot is obvious about 5e monsters from the Starter Set there are a number of areas we simply cannot break down until we have a larger sample size. Challenge Rating (aka CR) and Damage are the two key areas that present this difficulty.

Another problem resulting from the small sample of low level monsters is, of course, scaling to higher levels. The Starter Set does include creatures from CR0 through to CR8, but there is only one CR8 creature (the Young Green Dragon) and one CR4 creature (the Flameskull). The rest of the monsters range fairly evenly from CR0 through CR3. Until we can analyse a volume of higher level monsters we won't be certain of how our results scale or of any stepping or bumps needed along the way.

Finally, there is a downside to using a process-oriented build methodology. While these approaches generally have some resiliancy built into them the final result may still be significantly weaker or stronger than anticipated. There are ways to compensate for this or check against it, but these are difficult to discover with small sample sizes.

 

The Ugly

An analysis hoping to prove useful in the short term will need to deal with the issues described above. And this is where it gets a bit dirty. The only real option is to plainly flag where there's a shortfall, use a placeholder that seems appropriate and revisit the area once more data is available.

 

Where To From Here?

Based on the above observations and assumptions I decided to make a rough long-term plan for my D&D 5e monster analysis. This plan has five distinct phases...

1. Monster Construction. In this first phase we'll flesh out what I've explored of monster design, flagging items as described above. This phase will be driven primarily out of Basic D&D and the Starter Set. I expect it to last only a few short weeks and plan to make 2-3 blog posts a week during this period.
2. Preparation. Once the first phase is completed I will prepare for the deeper analysis the Monster Manual release will trigger. This will mainly consist of analysis of PC data, similar to the Class Analysis I did for my D&D Next series. During this time new official D&D 5e monsters may also be release and, if appropriate, I will post updates for the Monster Construction phase. Basic D&D and the Player's Handbook will be the main sources of this work. New blog posts will be few and far between during this period.
3. Monster Manual Data Entry. The day I get my hands on the new Monster Manual I'll be consumed with entering all of the monsters into a spreadsheet and doing the preliminary number crunching. Don't expect any blog posts during this period, but it will only last a couple of weeks.
4. Review. The first thing we'll do with our Monster Manual data is check our Monster Construction guidelines. We'll make any necessary corrections and fill in any gaps we can. Then we'll look to extend it to higher level creatures. This will probably take a couple of weeks.
5. Deep Analysis. Finally I'll embark on a much deeper analysis of monsters. The results of this will look similar to much of my D&D Next Monster Analysis. It's difficult to estimate how long this will take or how frequent blog posts will be. But the aim is to produce tables that support a result-oriented monster construction methodology.

 

Master Index

Master Index

Part 2: Before Building

D&D 5e Monsters: Master Index

The momentum of Surf's D&D Next Monster Analysis overflows into the 5e release and Surf pokes an analysis stick at D&D 5e Monsters...

 

I was fortunate enough to get access to part of the D&D 5e Starter Set several days in advance. The Appendix B: Monsters section from the Lost Mine Of Phandelver booklet is the key item of interest from a monster analysis perspective and with this in hand I was able to complete my initial analysis in very short order.

With the Starter Set released today it seemed like a good time to launch the 5e monster math articles!

Index

Here's a quick map of what the series covers...

• Part 1: Starter Set Monsters
• Part 2: Construction: Before Building
• Part 3: Construction: CR & Size
• Part 4: Construction: Ability Scores & HP
• Part 5: Construction: AC & Other Attributes
• Interlude: A Bunch Of Monsters!
• Part 6: Construction: Traits & Spellcasting
• Part 7: Construction: Damage
• Part 8: Construction: Actions
• Part 9: Construction: Attack Bonus
• Part 10: Construction: CR Evaluation
• Part 11: Construction Consolidation

Keep in mind that this is an intended map. As things progress our course may alter, but don't worry I'll keep this index up to date!

 

Part 1: Starter Set Monsters