Customized monsters and adjusting CR

[Felix]

Over in the Spiked Chain thread, a side discussion blossomed concerning the adjustment of monster CRs in the event that the monster was changed, modified, or optimized by the DM.

Obviously changing one of the Monster's skill ranks from Knowledge (12th Century German Poetry) to Perform (Interpretive Dance) won't affect the CR.

Obviously adding 20 levels of Fighter will.

So where in between the two extremes of monster customization does the CR adjustment/non-adjustment line lie? Does the CR remain constant but only the EL change when the PCs face it? How much wiggle room does one unit of CR possess?

Some examples:

Does switching skill ranks from something that doesn't affect combat to something that does rate a change?

Does optimizing feats for a particular class/weapon/tactic?

Does changing racial HD to classed HD?

Does adding NPC class levels?

Does re-arranging stats but maintaining the same point-buy total value?​

None of these things? A combination of these things?

And one hypothetical: you have an Environment: Mountains creature that is CR 8. It has three feats: Toughness, Great Fortitude, and Track. You swap those feats out for Kick Butt In Mountains, Improved KBIM, and Superior KBIM. You realize that this change makes the monster much more effective in mountainous areas and much weaker in non-mountainous areas. By doing this does the CR:

Remain constant, as does the EL?
Remain constant, though the EL will differ depending upon the environment it is encounter in?
Increase to reflect the increased difficulty when encountered in Mountains?
Decrease to reflect the decreased difficulty when encountered elsewhere?​

Where do you draw the line between the monster being more difficult, and the environment making the encounter (which only includes the monster) more difficult?

 

[Infiniti2000]

First things first: you cannot rationally compare swapping abilities with adding abilities. Changing out feats and skills for other feats and skills is obviously not the same thing as adding HD or class levels. I'm going to not bother responding to the addition of HD or class levels because I think that's suitably handled by the books. If you have a specific example, I'd be happy to discuss it, but in general we'll not get much further than the guidelines in the books.

Changing racial HD to class levels is an extremely significant change and one I strongly advise against. Actually, I so strongly advise against it that discussing a CR change because of it is irrelevant. If the DM is so confident in doing such a thing, then the on-the-fly gut-calculation of CR would be trivial by comparison.

As to whether the CR changes or the EL changes, I'm not sure I see the significance. How is the DM using these values to make the game fairer, or better? If the DM is considering optimizing monsters, then clearly the DM must be experienced. Thus, the CR/EL for purposes of experience points could be a retrospective endeavor (that's endeavour for Hyp).

Therefore, the only thing that is necessary is to gauge the encounter such that it doesn't overwhelm the party, or such that it presents the appropriate challenge desired at that point. The first and best indicator of how much the optimization changes anything is to determine how well the players have optimized their characters. If they are powergamers then by and large I wouldn't adjust any CR ever. I may retrospectively adjust the location-specific EL (i.e. add in a small, up to 10%, ad hoc XP bonus). If the PCs are relatively organic (i.e. not strictly powergamed), then I may consider adjusting the EL for any encounter that the monster is a part of.

 

[Felix]

First things first: you cannot rationally compare swapping abilities with adding abilities.

What's irrational about it?

I get that by adding even just a bonus feat, you are increasing the sum total of abilities by one feat, whereas by swapping feats, the number of feats remains the same. And some feats are more powerful than others, right? So how is swapping Toughness for Spring Attack less of a change than adding Skill Focus: Appraise?

Surely you shouldn't paint with such broad strokes?

Changing out feats and skills for other feats and skills is obviously not the same thing as adding HD or class levels.

Besides being the same thing in that you tailor the monster to your liking, you're right; same activity, different degree. Which is why I ask where between the extremes of changing one skill rank and adding 20 class levels should you begin to consider re-evaluating the CR.

Changing racial HD to class levels is an extremely significant change and one I strongly advise against. Actually, I so strongly advise against it that discussing a CR change because of it is irrelevant.

Uh, wow. Ok. I didn't know you felt so strongly about it. I feel like I ought not to have asked the question.

 

[Jhaelen]

I get that by adding even just a bonus feat, you are increasing the sum total of abilities by one feat, whereas by swapping feats, the number of feats remains the same. And some feats are more powerful than others, right? So how is swapping Toughness for Spring Attack less of a change than adding Skill Focus: Appraise?

You've basically already answered your question:

There is no general answer to your problem.

In an ideal world the CR would always be correct and all feats would be identical in power.
But we aren't living in an ideal world.

You'll have to look at the monster after making your changes and compare it to existing monsters. If you think it's now too tough or too wimpy for its previous CR, change it. Otherwise don't.

 

[Infiniti2000]

What's irrational about it?

...

Surely you shouldn't paint with such broad strokes?

Isn't the point of your query essentially to figure out how to paint with such broad strokes? Otherwise, please give the specific examples of swapping/adding that you're interested in and I'll be happy to comment on them. If you have no specific examples, then yes you're interested in generalities.

And, in general (most of the time except for some unusual circumstances) substitution does not equal addition.

Uh, wow. Ok. I didn't know you felt so strongly about it. I feel like I ought not to have asked the question.

The question on the whole is fine, but my comment there was in reference to only one of your hypothetical statements. I'm guessing you don't agree with my point, though? Feel free to rebut and I'd be happy to reconsider my stance. But, as of now I would strongly advising against something like replacing 3 racial HD of an ogre with 3 barbarian class levels. For one thing, it would be non-trivial in most cases to deconstruct the monster racial HD (stats, size, feats, skills -- which ones?), for another thing the other abilities, including the LA and CR, become screwed up. Are SPA and the like reformulated?

 

[Felix]

And, in general (most of the time except for some unusual circumstances) substitution does not equal addition.

I can't imagine you like words being put in your mouth, but I'd like that question answered...

So would you say that the line between changing CR and not lies between substitution and addition?

I'm guessing you don't agree with my point, though?

Not actually; I'm not pursuing an agenda here, man. I asked a question and felt chastized for doing so. I don't particularly care to rebut because I asked a question when I didn't know the answer (Novel!). Thanks for setting me straight.

 

[Nellisir]

I'd suggest reposting this query, or having a mod. move it, to the monster forum. You might get answers that are a little less...emotional - though, to be honest, the most accurate answer I can think of is "it depends".

 

[blargney the second]

Whenever I change a monster significantly, I do a manual eyeball to gauge its effectiveness compared to several other creatures in MM1 over a 3-CR spread.

 

[Felix]

Whenever I change a monster significantly

What all do you do to monsters when you change them?

Or have you done, I should say...

 

[blargney the second]

What all do you do to monsters when you change them?

Or have you done, I should say...

Anything I feel like to make the fight more interesting. We're at the end of an edition, so players know a lot about monster capabilities. Or so I like them to think...

I advance HD, add/change class levels, change feats, skills, spells, diddle with their ability scores, add templates, substitute special abilities (bye bye improved grab, hello anything else!), and throw in random bonuses and weaknesses to any of their stats.

At the end of the process, I just compare to stuff in the MM as well as the party's capabilities for a ballpark CR.