D&D 5E Advancing Monsters; still confusing

[Erdric Dragin]

So I'm reading the DMG in the monster creation section but I'm having a hard time figuring out how to advance a monster and excactly WHEN I should increase their Challenge Rating?

I'm having a Boar be the first battle for two of my kids playing the game in their first combat encounter. I want the Boar to have an AC of 13 instead of 11.

According to the DMG on pg. 274, if I increase AC by 2, then the CR goes up by 1 (or 1 step). So it should be CR 1/2 and not 1/4, if I do that, according to the rules. However, because its AC is 13 (which is the same as any creature CR 3 or less) does this mean I HAVE to increase it's HP to between 50-70 and its damage output to 6-8/round in order to match the CR 1/2 alongside the AC increase as per the table on pg. 274, or is the +2 AC good enough alone for the CR increase?

While I'm at it, is there a website with online tools that can calculate new CR if I input a creature's stats in myself? That'd be the easiest route I guess.

 

[Charlaquin]

I believe a boar with 13 AC would still be well within the CR 1/4 range. CR is not an exact science, and little fluctuations like that are pretty tolerable. Since you asked though, here’a an online tool for entering stats and calculating CR I found with a quick google search: CR Calculator - 5etools,

 

[Ath'kethin]

CR is calculated in two steps: defensive CR and offensive CR. The final CR is the average of the two.

That makes it sound much simpler than it really tends to be, especially since the following pages of that section in the DMG have a host of other factors that can change the values.

For your boar, boosting its AC to 13 won't change its CR.

By the numbers: 11 HP falls into CR 1/8. AC 13 does not change this value.

4 damage per round falls into CR 1/4. The attack bonus does not change this value.

1/4 + 1/8 = 3/8, ÷ 2 = 3/16, which can still still round to 1/4. So no change there.

HOWEVER, on page 280 we see and adjustment for the Charge trait and on page 281 we see an adjustment for the Relentless trait. Let's see what they do.

The damage value on the table is the average damage the monster inflicts per round, based on a three round cycle. The boar normally deals 4 damage per round with it's tusk (4+4+4)/3=4 damage average; if we add 3 damage to one round for the charge trait it becomes (4+4+4+3)/3=5 damage average. This ALSO falls I to CR 1/4 territory, so no real change to the earlier math.

For Relentless, we adjust the monster's effective hit points based on its expected CR. Since the CR we are expecting (or at least what we started with) is less than 1, we can just use the value for CR 1, which is 7 HP. Adding 7 hp to the boar's 11 HP gets us an effective hp total of 18, which still falls into the CR 1/8 range on the table. So no change there.

In short: boosting the boar's AC to 13 does not change its Challenge rating.

To my knowledge, there is no online calculator to do all this. And it does take some getting used to (especially remembering to check pages 280 and 281).

Also note that many monsters in the Monster Manual, if you run the math based on the DMG section, seem to have incorrect Challenge Ratings. That's partially based on playtesting results and partly due to the fact that the MM came out before the DMG and not all the tools were perfected yet. But it mostly illustrates that the concept of CR is inexact at best and has some wiggle room.

 

[Charlaquin]

Also note that many monsters in the Monster Manual, if you run the math based on the DMG section, seem to have incorrect Challenge Ratings. That's partially based on playtesting results and partly due to the fact that the MM came out before the DMG and not all the tools were perfected yet. But it mostly illustrates that the concept of CR is inexact at best and has some wiggle room.

Which goes to show that the designers probably didn’t actually use the system in the DMG; they probably arrived at the stats in the MM through a combination of loose guidelines, gut feel, and playtesting, and later reverse-engineered a set of rules that would systematically produce stats and CRs similar to what they had developed for the MM.

In other words, don’t worry too much about following the system in the DMG to the letter. It’s a useful guideline, but it won’t ruin the game if you fudge things here and there.

 

[jgsugden]

The rules for advancing CR are not an exact science. An improvement of 2 to ACis very different when going from 11 to 13 or 18 to 20. My suggestion: Don't bother.

Instead, look up a monster with a similar 'role' that is at the CR you want, and then take the iconic abilities of the monster you want to use and put them on the form of the one that is at the right CR. If you see something that looks wrong to you after the switch, make tweaks until it feels right - and you'll almost always be just fine.

The game will not break if the creature you make is actually more of a CR 2 monster than a CR 1/2. You're unlikely to end up with a monster that they can't beat withiut you realizing it.

 

[cbwjm]

Advancing monsters is something that previous editions did a lot better, especially the monster builder for 4e that did all the calculations for you.

If boosting monster stats in 5e, I wouldn't worry too much about CR unless your doing some widespread changes. Rather than boosting AC, I'd probably boost hit points, they have a dice range for hit dice so I'll sometimes use that and just max the creatures hit points to make them a little tougher. I'd keep CR the same if doing this, only upping CR if I increased hit points, AC, and potential damage by a significant amount.

 

[MNblockhead]

While I'm at it, is there a website with online tools that can calculate new CR if I input a creature's stats in myself? That'd be the easiest route I guess.

Herolab Classic will and gives some basic warning when damage output, AC, etc. don't match with CR.

Not sure if the online version of HL does this or even if the online version support 5e yet.

This is something the D&D Beyond should provide. It would be great if DDB's monster creation functionality was as advanced as its character creation ability.

 

[dave2008]

So I'm reading the DMG in the monster creation section but I'm having a hard time figuring out how to advance a monster and excactly WHEN I should increase their Challenge Rating?

I'm having a Boar be the first battle for two of my kids playing the game in their first combat encounter. I want the Boar to have an AC of 13 instead of 11.

According to the DMG on pg. 274, if I increase AC by 2, then the CR goes up by 1 (or 1 step).

That is incorrect. The defensive CR goes up by 1 step. That is only a half step for the whole CR: (defensive CR + offensive CR )/ 2

Now about already has low HP and AC for a CR 1/4 monster. So this half step is probably insignificant. I wouldn't change the total CR are all.

So it should be CR 1/2 and not 1/4, if I do that, according to the rules.

As explained above that is incorrect.

However, because its AC is 13 (which is the same as any creature CR 3 or less) does this mean I HAVE to increase it's HP to between 50-70 and its damage output to 6-8/round in order to match the CR 1/2 alongside the AC increase as per the table on pg. 274, or is the +2 AC good enough alone for the CR increase?

No, you do not need to add HP, that is not how the table works. It is a give and take.

While I'm at it, is there a website with online tools that can calculate new CR if I input a creature's stats in myself? That'd be the easiest route I guess.

Yes, there are some. I will see if I can find one.

EDIT: I was mistaken. The tools I found help make a pro-looking stat block, but they do not calculate CR.

 

[aco175]

I try and not figure out too much math beyond HP and fireball damage in D&D. I tend to wing it and boost where I like and maybe look at another similar monster for some guidance. The biggest problem space is between CR1 and CR2 where there should be some sort of CR1.5

Like what others said, do not become too tied up in rules and numbers that you become frustrated and skip the fun part.

 

[NotAYakk]

I'm going to plug my "Ridiculously Simple Monster Building": D&D 5E - Ridiculously Simple Monster Building

You can treat each step under CR 1 as 4 less Monster Building Points (as in, CR 1/2 is CR 0, CR 1/4 is CR minus 1, CR 1/8 is about CR minus 2). Each CR is 4 MBP.

(When I plug DMG sample stats for CR 1/2, 1/4 and 1/8 I get 14, 10 and 8 MBP. The above rule is 14, 10 and 6, which is pretty close.)

So adding 2 AC is 2 MBP, or half a step. If you want a full step, add another 16 HP, or 6 DPR, or some combination.