Advancing a creature and revising CR

[enworldatemylogin]

I haven't actually tried calculating this myself, though I guess when I'm finished advancing the monster I'll see how it works, but to get the new challenge rating do you just do as it says in the MM appendix, i.e. add based on new HD and added abilities or should you recalculate based on the new hit points and everything as a whole?

I haven't thought of this before and I'm wondering what to do.

 

[Pinotage]

By and large the rules presented in the DMG work, although there will be instances where the CRs will be off when advancing a monster. Essentially you just advance the monster with as many HD as you like, and adjust the CR based on this increase (with respect to type are presented in the DMG), and size increases (if any). You may feel that you want to tweak the CR depending on the result, though.

For example, a dire wolf is CR 3 and has 6 HD. Advancing it to 12 HD means an increase in 6 HD but no size increase. The DMG states +1 CR per 3 HD, so the CR increases from 3 to 5. That's the correct CR according to the DMG. You can take a look at the dire wolf now, and compare it to, for example, a level 5 fighter. The dire wolf had 90 hp, AC 14, +16 Bite Attack for 1d8+11 Damage (excluding ability increases with added HD), and two more feats. Overall, it seems reasonable for CR 5, although some might want to push it to CR 6.

The thing to remember is that CR is really a guideline. Some parties are also stronger or weaker than others, and naturally party size also affects things.

Pinotage

 

[shilsen]

What Pinotage said, except that he keeps calling the MM the DMG

In my experience, when advancing by hit dice, creatures tend to be a little strong for the CR that the MM suggests, esp. for some of the creatures where it recommends that they advance 4HD for a +1 CR improvement. But, as Pinotage noted, as long as you treat CR as the guideline that it is and remember the context of your particular game and group of PCs, you should be fine.

 

[Voadam]

I haven't actually tried calculating this myself, though I guess when I'm finished advancing the monster I'll see how it works, but to get the new challenge rating do you just do as it says in the MM appendix, i.e. add based on new HD and added abilities or should you recalculate based on the new hit points and everything as a whole?

I haven't thought of this before and I'm wondering what to do.

There is no real base calculation given for recalculating based as a whole, those are rules solely for advancing a creature from the base stat block with an existing CR, not for assigning a CR to a wholly new creature.

 

[Aestolia]

I was actually looking at this last night as well.

In terms of new or created monsters, MMI outright says

"yeah... um... find a monster that's about as powerful as yours... use that CR... that should work."

 

[eamon]

I was actually looking at this last night as well.

In terms of new or created monsters, MMI outright says

"yeah... um... find a monster that's about as powerful as yours... use that CR... that should work."

Exactly. Compare your generated monster to others in the MM as a baseline.

I run an extensive campaign with many many NPC's and advanced monsters (perforce, I made the mistake of taking a published adventure below my party level and then "just fixing" all the CR's... oh boy...).

So with all that experience with NPCs, the only thing that works well is comparison to the MM.

Specifically: I recommend against comparing them to an NPC of that level. Just like the monster guidelines are rough, the NPC guidelines are too. Two NPC's of the same level definitely don't always have the same CR, and generally, the real challenge is usually lower than the guideline would suggest (IMHO). Further, a 5th level fighter is an extremely variable being due to equipment choice, feat choice etc. In general, (N)PC's tend to have more AC, fewer dramatic, permanent special abilities (like regeneration), fewer hitpoints, and higher saves - and that makes apples to apples comparisons needlessly difficult. Just take a similar monster from the MM and look at that. In case of an advanced dire wolf, take a look at the dire lion. Indeed it looks a little weaker than a 12HD Dire Wolf, although it does have pounce, which is a very useful ability. In general, when mechanically advancing by HD, that's a recurring pattern; the result will have too much hitpoints and base attack, but too few special abilities of too low a level. And as any druid summoner can tell you, a dire wolf is pretty strong already, so it comes as no surprised that advanced versions are tough. If you compare if to an Umber Hulk Zombie (107hp, AC 19, +14 attack bonus, DR and undead immunities), then it's not looking as bad. You could make it CR 6 without too much problem.

Given the way CR's add up, a given challenge rating should be about as powerful as a real PC - with all bonuses due to min-maxing, high wealth, and everything - of that level, and NOT as strong as an NPC (otherwise, the higher level you become, the easier the game gets, whereas often the opposite is the case using MM monsters!).

In short, compare to monsters, not NPCs.