How does one assign a Challenge Rating?

[Frosty]

I was looking through monsters from different monster manuals and different books, and I'm having a hard time figuring out a way to assign CRs. there just doesn't seem to be any consistency. For example, how is that Giant Crab comparable to other CR3s or a Fleshraker to other CR2s? Looking on the other end of the scale, a Balor is CR20 yet Malconthet, the Queen of the Succubi with 415 HP, save DCs in the high 30s, scary-ass (Su) and (Sp) abilities and has similar combat damage is only a CR21?

How exactly is CR determined anyways? Is there some sort of formula for it or did WotC just eyeball things...while very drunk? I will be tyring to design some new devils on my own, and I'll need help with assigning their CR.

[kamikasei]

Arbitrarily and badly. But there are suggested guidelines on the homebrew forum.

I've seen a variety of methods to set CRs on creatures, but I've really only found two that work 95% of the time. The first is the one I use: the creatures CR should be between a 3:2 to a 1:1 ratio for BAB:CR, generally, so that a BAB of +9 would be a CR between 6 and 9.

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A challenge rating is how tough an encounter with this beast will be. Generally a creature of, say, a CR of 5 should be a standard challenge for a party of 4-5 5th level characters. To defeat this creature will cause them to use up roughly 1/4th to 1/3 their daily resources such as spells, potions, etc. This depends on the build of the party, their items, terrain, and many other factors, but in general it is more or less accurate.

Figuring out this challenge rating is the real fun part, and probably the most challenging bit of monster making. Its as much guestimating as anything, and there are no true rules to determine it exactly. Here is the closest method I've been able to come up with, though creatures with an enormous ammount of hit points or really low-leveled creatures will still be innacurate. The best way is to play-test the creature with parties of varying CR and find out which one most closely fits. Here though is the guestimator method:

#1. Divide creature's average HP by 4.5 to 6.5.
4.5 for 5 HD or lower, 5 for 6-10 HD, 5.5 for 11-15 HD, 6 for 16-20 HD., 6.5 for 20-25 HD.

#2. Add 1 for each five points above 10 its AC is, subtracting 1 for every 5 below.

#3. Add 1 for each special attack (+2 to +5 or more if its got a decent number of spells in its spell-like abilities).

#4. Add 1 for each quality unless you deem it worthy of more. Add 1 for each resistance and 10 points of DR it has, and 2 for each immunity. Subtract 1 for each vulnerability.

#5. Add 1 for every two bonus feats it has.

#6. Divide total by 3. This should be its rough CR.

[Duke of URL]

I usually just guess, but then again, creature design is not one my strengths.

[mostlyharmful]

did WotC just eyeball things...while very drunk?

Do you really have to ask?

Sarcasm aside CR depends on the capabilities of your PCs, to be honest eyeballing it with specific details of the campaign and Characters in mind is about the only way that makes sense.

[Starsinger]

The standard method is to guess until you get it right, kinda like spellschools, IMO.

[Frosty]

I don't want to have to test it out on my party. Because then they might die from it. I mean, it just seems wrong than a level 22 Warrior has the same CR as Malconthet. They are CLEARLY not the same strength. I'm not sure any non-full-caster character at level 20 can really challenge the likes of her, while there are PLENTY of builds that can just pwn the level 22 Warrior.

[afroakuma]

Take some of the DMG's generic NPCs and run a simulated combat. Often works for me.

But yeah, CRs, even *cough*especially*cough* WotC's own, are often a major crapshoot. MMII's Hellfire Wyrm, a spellslinging hell dragon, has the same CR (26!!!) as MMII's Mountain Giant, a really big giant who can... is really big.

One suggestion I read somewhere: Create monster, assign CR where you want it to be, then adjust the monster until it matches your desired CR.

[Frosty]

Take some of the DMG's generic NPCs and run a simulated combat. Often works for me.

But yeah, CRs, even *cough*especially*cough* WotC's own, are often a major crapshoot. MMII's Hellfire Wyrm, a spellslinging hell dragon, has the same CR (26!!!) as MMII's Mountain Giant, a really big giant who can... is really big.

One suggestion I read somewhere: Create monster, assign CR where you want it to be, then adjust the monster until it matches your desired CR.

But how do I know if the monster needs adjusting to say...fit the CR15 I want? DMG generic NPCs are in no way shape or form representative of the PCs, imo. They kind of...suck.

[insecure]

I don't want to have to test it out on my party. Because then they might die from it. I mean, it just seems wrong than a level 22 Warrior has the same CR as Malconthet. They are CLEARLY not the same strength. I'm not sure any non-full-caster character at level 20 can really challenge the likes of her, while there are PLENTY of builds that can just pwn the level 22 Warrior.

Keep in mind that NPC classes only have half the CR compared to a PC class at the same level.

[Frosty]

Keep in mind that NPC classes only have half the CR compared to a PC class at the same level.

I remember reading that NPC classes have PC class minus 1 for CR?

[Prometheus]

The easiest means is to take an existing creature and mod the crap out of it.

The official means of determining CR is to test against a standard party (equivalent to what is in the DMG for PC NPCs rather than your more typical optimized), (roles: melee, skillmonkey, healing, and magic). Of course, this is the same system they used to generate the Monster Manuals and set up class balance.

Vorpal Tribble's (already posted) works pretty well.

[Frosty]

Perhaps when WoTC tested their monsters they had evocation specialist Wizards, healbot clerics, Sword and Board Fighters, and non-multiclass rogues?

[Starbuck_II]

I was looking through monsters from different monster manuals and different books, and I'm having a hard time figuring out a way to assign CRs. there just doesn't seem to be any consistency. For example, how is that Giant Crab comparable to other CR3s or a Fleshraker to other CR2s? Looking on the other end of the scale, a Balor is CR20 yet Malconthet, the Queen of the Succubi with 415 HP, save DCs in the high 30s, scary-ass (Su) and (Sp) abilities and has similar combat damage is only a CR21?

How exactly is CR determined anyways? Is there some sort of formula for it or did WotC just eyeball things...while very drunk? I will be tyring to design some new devils on my own, and I'll need help with assigning their CR.

The Giant Crab is known to be low balled in CR. It should be higher.

[Chronos]

The best method, if you've got the time, is to construct a "standard" party of four characters, and run a few test fights between the party and the monster for each level of the party. When the party of level X beats the monster without too much difficulty, but the party of level X-4 gets wiped out about half the time, you've got it.

Perhaps when WoTC tested their monsters they had evocation specialist Wizards, healbot clerics, Sword and Board Fighters, and non-multiclass rogues?

That seems to be the concensus. So if you're trying to match the CRs of published monsters (such as they are), that's more or less the party you should be using. Then remember that your players are probably using something better, and shift everything that they're fighting (published and homebrew) by a few CRs.

[mostlyharmful]

I remember reading that NPC classes have PC class minus 1 for CR?

Oh? so the level 22 Warrior is CR 21? And this is significantly better?

[Frosty]

Oh? so the level 22 Warrior is CR 21? And this is significantly better?

I didn't say I agreed with the formula, but I remember the DMG saying it. Frankly, I'm not sure about the whole: a Level X PC is a CR X challenge.

It implies that two CR X creatuers are about as tough as each other, and I'm pretty sure that most level 21 characters are NOT the equivalent of Malconthet, and most level 20 characters are't the equivalent of a Balor.

[FMArthur]

The Giant Crab is known to be low balled in CR. It should be higher.

I can't even remember the last time I saw THAT DAMNED CRAB referred to by its official name, Giant Crab. Took me a while to find it when I first heard of it because I didn't know its real name, just That Damned Crab. Apparently a source of many horror stories of early-campaign unplanned TPKs.

[Frosty]

I can't even remember the last time I saw THAT DAMNED CRAB referred to by its official name, Giant Crab. Took me a while to find it when I first heard of it because I didn't know its real name, just That Damned Crab. Apparently a source of many horror stories of early-campaign unplanned TPKs.

I wonder where that nickname came from.

[Sstoopidtallkid]

I wonder where that nickname came from.

Yeah, it doesn't seem applicable at all.

@the OP:Here's WotC's method, as I understand it:Get a mini of every monster you want to assign a CR to. Superglue a spike to the top of each mini. Get a dartboard. Get a blindfold. Get really, really drunk. Throw. The resulting score is the CR of the mini.

[kjones]

For creating monsters with a CR of 1-20:

1. Follow closely the guidelines set down for advancement in the SRD.
2. Cross-check with Vorpal Tribble's rules of thumb - adjust as necessary. I recommend a geometric mean as a method that maintains proper mathematical weight between the two.
3. Playtest repeatedly with a set of generic PCs. If necessary, playtest with your actual party. You'll want to do this at least ten times, for optimum statistical merit.
4. Throw away all the data you've just collected.
5. Roll 1d20. The result is the creature's CR.

EDIT: I... can't believe this suggestion was essentially just ninja'ed.

[Eldariel]

That Damn Crab has the annoying feature that it's immune to all ways of solving physically tough encounters on that level. Amusingly enough, for example a Purple Worm is not. So I'd be more frightened by That Damn Crab than Purple Worm on level 3 (and yes, I've been in a party that killed a Purple Worm on level 3 [Touch of Idiocy] - incidentially, the last party that faced The Crab experienced a Near TPK with the Wizard Alter Selfing into Avariel and getting the heck out of there; last time I pit a Crab vs. level 3 party...).

[Frosty]

Maybe pit the crab against a level 6 party? The raging barbarian with 26 strength and Improved Grapple has an ok chance I guess...

[Eldariel]

Eh, the way to beat it is still to stay the hell out of the grapple. But a level 5 party could have a decent chance; with some form of transportation spells, Level 3 Stance (Roots of the Mountain), just plain higher AC and AB, access to flight and so on, a level 5 party is well equipped to defeat it (obviously it'll submerge if you take flight, but that's enough to "win" the encounter). Level 6 means you can have Shock Troopers and they can probably one-shot it as it has a low AC. So it isn't that scary, it's just scary for a level 3 party since it's physically tougher than any normal level 3 characters and immune to most Magic.

[Starbuck_II]

Maybe pit the crab against a level 6 party? The raging barbarian with 26 strength and Improved Grapple has an ok chance I guess...

I think that the Crab is kinda CR 5ish. I mean, that would be when most parties can beat the thing only using 20% resources.

[Frosty]

Eh, the way to beat it is still to stay the hell out of the grapple. But a level 5 party could have a decent chance; with some form of transportation spells, Level 3 Stance (Roots of the Mountain), just plain higher AC and AB, access to flight and so on, a level 5 party is well equipped to defeat it (obviously it'll submerge if you take flight, but that's enough to "win" the encounter). Level 6 means you can have Shock Troopers and they can probably one-shot it as it has a low AC. So it isn't that scary, it's just scary for a level 3 party since it's physically tougher than any normal level 3 characters and immune to most Magic.

Shock Trooper? You're going to lower your AC when your charge will provoke an AoO, allowing it to hit you adn then use it Improved Grab to stop your charge?

[Sstoopidtallkid]

A good chunk of the problem with the CR system is that there's so many invisible lines where something goes from 'no challenge' to 'TPK'. The Crab, for instance, can TPK any 4th level or lower party. A 5th level party can win, but will have trouble, and may lose a member. By 6th level, it shouldn't take many resources at all to beat TDC. There is no CR that's appropriate for that.

[Frosty]

But where is that line and how can I avoid it when designing monsters? I want to design cool, memorable, and challenging encounters without it turning into a TPK.

Back to the Giant Crab, a party is supposed to wipe 50% of the time against a creature of their average party level + 4 correct? If the crab wipes a level 3 party almost 100% of the time, then doesn't that mean it's above CR 7?

[Eldariel]

Shock Trooper? You're going to lower your AC when your charge will provoke an AoO, allowing it to hit you adn then use it Improved Grab to stop your charge?

It's Large. You have a Reach Weapon. You're not provoking.

[Sstoopidtallkid]

But where is that line and how can I avoid it when designing monsters? I want to design cool, memorable, and challenging encounters without it turning into a TPK.

Back to the Giant Crab, a party is supposed to wipe 50% of the time against a creature of their average party level + 4 correct? If the crab wipes a level 3 party almost 100% of the time, then doesn't that mean it's above CR 7?

Except a level 6 party can kill it easily, and a solo Warrior at level 10 can crush it. That's the problem, some creatures just aren't able to be statted well.

Heck, if you really want a TPK, Venerable Dragonwrought Kobold Adept 4. CR1. Make the party beg for mercy.

[Starbuck_II]

But where is that line and how can I avoid it when designing monsters? I want to design cool, memorable, and challenging encounters without it turning into a TPK.

Back to the Giant Crab, a party is supposed to wipe 50% of the time against a creature of their average party level + 4 correct? If the crab wipes a level 3 party almost 100% of the time, then doesn't that mean it's above CR 7?

Glitterdust, Grease, and running work. It only has a 40 speed on land! Dude, it is as fast as a Barbarian in light armor (or naked monk).

Glitterdust because it has low Will saves and Glitterdust isn't affected by vermin traits.
But that won't last long and it stills have 66 hps!

Still a Level 5 party shouldn't lose.