CR Handbook

[J-H]

I can't find a CR or CR-adjustment handbook thread. Are there any must-read threads on the topic?

I'm using the d20SRD encounter calculator so far for XP awards, but it seems to swing wildly between "Easy" and "Very Difficult" on how it judges CR vs group ECL. Also, I'd like to get a bit more granular about how much making minor changes (like adding armor) to creatures bumps their CR.

I know I can recognize some of the under-CR'd stuff, but I'm sure I'll overlook some. I know I didn't expect a wussy 2HD Darkmantle to hit for 15 points of damage in 1 round (attack, then constrict).

[Big Fau]

I can't find a CR or CR-adjustment handbook thread. Are there any must-read threads on the topic?

I'm using the d20SRD encounter calculator so far for XP awards, but it seems to swing wildly between "Easy" and "Very Difficult" on how it judges CR vs group ECL. Also, I'd like to get a bit more granular about how much making minor changes (like adding armor) to creatures bumps their CR.

I know I can recognize some of the under-CR'd stuff, but I'm sure I'll overlook some. I know I didn't expect a wussy 2HD Darkmantle to hit for 15 points of damage in 1 round (attack, then constrict).

Often times it's a matter of knowing how optimized your PCs are, and understanding the intended tactics the monsters are supposed to use. A standard Mind Flayer, for example, is a flat-out rocket tag encounter that is either trivially handled (even with the flayer being fully buffed by it's powers/spells) or TPK-material (that Stun has a stupid duration). Commonly, if the encounter is composed of a single sac of HP against 4 mid-op players (as a lot of premade modules will have), lower the CR of the monster a few points. That kind of encounter is often over quick. Conversely, if the monster triggers an ability that normally doesn't occur (your constrict), the monster has done its job for its CR.\

Constrict is one of those rare abilities to trigger. Most (frontline) PCs happen to have a decent grapple modifier, so anything in their size category isn't going to get that effect off very often unless that enemy is hyper-specialized. If you want to see an example of a good grappler for its level, the Monstrous Crab from Stormwrack is known to absolutely destroy PCs in a matter of rounds.

[HolyDraconus]

Often times it's a matter of knowing how optimized your PCs are, and understanding the intended tactics the monsters are supposed to use. A standard Mind Flayer, for example, is a flat-out rocket tag encounter that is either trivially handled (even with the flayer being fully buffed by it's powers/spells) or TPK-material (that Stun has a stupid duration). Commonly, if the encounter is composed of a single sac of HP against 4 mid-op players (as a lot of premade modules will have), lower the CR of the monster a few points. That kind of encounter is often over quick. Conversely, if the monster triggers an ability that normally doesn't occur (your constrict), the monster has done its job for its CR.\

Constrict is one of those rare abilities to trigger. Most (frontline) PCs happen to have a decent grapple modifier, so anything in their size category isn't going to get that effect off very often unless that enemy is hyper-specialized. If you want to see an example of a good grappler for its level, the Monstrous Crab from Stormwrack is known to absolutely destroy PCs in a matter of rounds.

In two rounds, in fact. I can personally attest to that.

[LTwerewolf]

I've personally found CR to be pretty useless when making encounters.

[J-H]

Yeah, I'm avoiding That Crab.

The darkmantles were placed on the map before the party started acting... high up, in the dark, with good hide modifiers vs bad spot rolls. They moved closer, then attacked right as somebody spotted some bones on the ground and looked up. 4 darkmantles against a 6-man party, and one of them landed on the halfling rogue and another on the dread necromancer - two of the three weakest grapplers. They were the closest targets.

The other two landed next to a paladin and a DFA respectively. You can guess how long they lasted.

I'm at an encounter right now with 9 humanoid opponents, and they all were given time to prep - so they all have armor that's not on the MM entry. +3 ac isn't worth a CR increase for 1 enemy, but x 9 it's a substantial boost.

This will be the 3rd encounter for the party so we'll see how it plays out. Aside from a single cone attack by a construct, it'll be the first time I've had spells or martial maneuvers play out against them too.

[Fizban]

Some people have made charts of expected values for hp/AC/AB and so on for monsters and PCs, but that's still a matter of opinion (though later editions have official tables). As Big Fau said (and I have belabored in many threads by now), it's up to the DM to figure out how threatening the monsters actually are. You have all the numbers, you can see the best and worst case scenarios, you can figure out the odds and what adjustments may be needed. First rule of encounter building: don't use anything you don't understand. Constrict looks tame at first but is ridiculously strong once you figure out how it actually works, remember that whenever you look at a new monster.

I'd first suggest making sure you know what the CR values are supposed to mean, and not relying on encounter calculators because they use the poorly chosen category names. Read through that section of the DMG carefully and pay attention. The important part is that a while CR=level monster is considered "challenging" against a 4 person party, it is not in any way a fair fight: that monster is outnumbered 4-1 and is considered threatening only because it has a chance of possibly killing one person (calling it "challenging" was a poor decision on the part of the designers, but I feel like they didn't want to advertise the true intent). The Darkmantle example seems pretty good there, a successful constrict can drop someone at the appropriate level, but one person's the best it'll do. A group of lower CR monsters with an equivalent ECL (say, a pair at level-2) might not be outnumbered but are instead significantly outgunned and should be expected to die easily.

Basically the CR system is not built around fair fights: it's built around the PCs avoiding fair fights as much as possible, with maybe one even fight and maybe one boss fight at each level. This seems to be how the game was expected to go in the olden days except then it was just how everyone played in order to survive, while here it's taken into account by the CR system itself. This lets the DM know how much combat they can force or where they should draw the lines when planning how the players can break up an enemy camp.

So back to those encounter calculator results: that's the section under Difficulty at the end of page 49. As I said above, "challenging" is actually a fight that should consume at most 20% of their resources (as mentioned under What's Challenging? on the same page), and only has a chance of killing one person, most likely due to luck or player error. "Easy" fights are actually so easy that many people just mark off a spell and skip the fight to save time. "Very difficult" results on the calculator are the least informative, as that covers a range from level+1 (barely more dangerous than "challenging") to level+4 (an actual 50/50 fight which can go TPK with bad luck/error), and this is probably why your results feel so swingy: you're getting encounters with an Encounter Level of party+1 which aren't actually all that hard but technically fall under "very difficult" so that's what the calculator tells you. I don't think anyone has trouble figuring out "overpowering."

Apart from that lecture and checking for best/worst scenarios, you can also eyball things based on how optimized your party is. If they're playing vanilla, don't mess with stuff. If they're running complicated builds and know exactly what they're doing, you can probably optimize all sorts of stuff to catch up and they'll deal with it, but that still doesn't remove the need to check your odds.

[Inevitability]

There was a thread that attempted to fix MM2's CRs, which are notorious for their extreme wonkiness (something something adamantine horror). Here's (http://www.giantitp.com/forums/showthread.php?187046-That-s-ONLY-CR-9-Let-s-Read-The-Monster-Manual-II) a link.

The thread itself didn't get very far, but it did use Vorpal Tribble's CR calculator, which is nice to get a general feel of a monster's strength.

[J-H]

Thanks, keep 'em coming.

I have the party at max HD but am playing monsters and summons out of the MM so far (high average); the squishiness difference seems like it takes a point off of the EL value for each whole encounter. If I'd had the first two encounters at max HP, they'd have lasted an extra 1-2 rounds each.

[OldTrees1]

I can't find a CR or CR-adjustment handbook thread. Are there any must-read threads on the topic?

I'm using the d20SRD encounter calculator so far for XP awards, but it seems to swing wildly between "Easy" and "Very Difficult" on how it judges CR vs group ECL. Also, I'd like to get a bit more granular about how much making minor changes (like adding armor) to creatures bumps their CR.

I know I can recognize some of the under-CR'd stuff, but I'm sure I'll overlook some. I know I didn't expect a wussy 2HD Darkmantle to hit for 15 points of damage in 1 round (attack, then constrict).

Well step 1 could be making the WotC CR calculation more intuitive. It basically follows 3 principles:
1: 2 Monsters of CR "X" are about as tough as 1 Monster of CR "X+2"
2: A pair of Monsters of CR "X-1" and CR "X+1" are about as tough as 1 Monster of CR "X+2"
3: Encounter Difficulty is decided by comparing the share of the encounter that 4 PCs receive.

Mathy Example: 6 5th level PCs vs 4 CR 4 monsters
Step 1: 4 CR 4 monsters ~= 2 CR 6 monsters ~= 1 CR 8 monster
Step 2: 1 CR 8 monster ~= 1 CR 5 monster + 1 CR 7 monster ~= 1 Cr 5 monster + 2 CR 5 monsters = 3 CR 5 monsters
Step 3: 3 CR 5 Monsters per 6 PCs ~= 2 CR 5 Monsters per 4 PCs ~= 1 CR 7 Monster per 4 PCs.
Conclusion: So this is going to be a CR only 2 higher than the Party level. Not an easy fight but not a boss battle either.


But WotC is fallible so that is not the entire picture (although it is a decent start).
1) WotC might assign the wrong base CR to a monster.
2) The first 2 principles cannot both be exact. If you cycle through them enough times you can result in a different estimate.
Ex: 4 CR 4 -A> 1 CR 8 -B> 1 CR 5 + 1 Cr 7 -A> 3 CR 5 -B> 3 CR 2 + 3 Cr 4 -A> 1 CR 2 + 4 CR 4
3) The base CR does not include augmentations/terrain/other factors. These are really too many and too varied to systematically quantify.

[Thurbane]

Unfortunately it's trivially easy to break CR in either direction.

CR is OK to use as a guide, but you have to know your party's strengths and weaknesses, as others have commented.

...this in turn depends on how experienced the DM is, and possibly one of the toughest learning curves. You can accidentally TPK your party with what looks on paper to be a totally reasonable encounter by CR; or you can throw something at them you expect to be a hard challenge, and they'll curbstomp it.

[Big Fau]

Unfortunately it's trivially easy to break CR in either direction.

CR is OK to use as a guide, but you have to know your party's strengths and weaknesses, as others have commented.

...this in turn depends on how experienced the DM is, and possibly one of the toughest learning curves. You can accidentally TPK your party with what looks on paper to be a totally reasonable encounter by CR; or you can throw something at them you expect to be a hard challenge, and they'll curbstomp it.

Yeah. Going by pure RAW CR is a bad idea due to non-associated class levels.

[Fizban]

Non-associated class levels are in a section about modifying monsters covered in warnings that it's dangerous and can produce unexpected results. The natural expectation is that the base CRs for everything is accurate, which is where the problem starts. The DMG does not do a good enough ( hardly any) job explaining how party dynamics and player ability can change the game. It explains pretty well how much risk there's supposed to be, but not how to evaluate the game to determine your risk.

I didn't either, so here's some more. The percentages are easy, just multiply the range of numbers that hit by 5% (so 16-20 is 25%, or 9-20 is 60%). Take the average damage per round, multiply it by the accuracy, and you have an idea of how many rounds it takes for the attacker to down their target. Spells that use attack rolls work out the same. It's easy to evaluate simple changes: giving a monster better armor makes it harder to hit. If the fighter needed a 10 but now he needs a 14, he's gone from 50% accuracy to 30% accuracy. If he can kill it in one round with luck, he needs two on average, +4 AC increases this to three rounds, he can still get lucky but that's a whole extra round or even two if he's not. Then we consider bigger spells: most spells either do something, or don't. Generally a successful spell will swing the battle hugely in the PC's favor, while a failed spell will either do nothing or a bit of damage. You take the chances that the spell works (usually what people need to roll to make their save), and there you go.

And then there's tactical evaluation. I generally consider four scenarios: best case where the players make all the right moves as if I'd told them ahead of time or they just knew the metagame, worst case where they make the wrong moves, expected case where they do whatever I've come to expect from them as individuals, and brute force where they just go all out (usually in an attempt to recover from worst case). Best case includes things like making sure you don't miss any full attacks, using the best spells for the job, fighting opponents in the correct order, and so on. Worst case means wasting spells, eating AoOs, not getting full attacks, and most importantly wasting whole turns. In my experience it's quite common for players to simply do dumb **** that basically means they've wasted their turn, and if you've got an encounter where someone wasting a turn is going to get them killed, don't be suprised if they all die. This is why you just can't have every fight be a serious threat, because even without bad luck players will eventually get stupid without any help.

Putting it together, the combat characters should be losing the damage race on their own: they're only part of the party. Every fight should require the use of at least a spell or two of significant level, from both casters, and if no spells are used should probably burn at least one frontliner's hp close to zero (a "challenging" encounter uses 20% resources and has a chance of killing one person: refusing to cast spells means it's all on luck and the fighter's hp, so he should end up very low or die fighting on his own-if he were a party of one the encounter would be 50/50). Buff spells are still spells though, so a fight that's won handily through buffed brawlers is still worth xp for all. Once you've got the grip on damage, spell use is estimated when considering your best/worst/expected/brute scenarios, where you can check what it does to damage. The fighter can't take these two guys alone because they out-damage him, but the cleric's buff will let him take them one on one, the wizard can probably shut one down first turn, and the rogue can kill that guy before the spell wears off, so best case is good. Worst case they do nothing and he's a dead man, but he's tough enough to last a round or two if the party gets dumb, worst case is non-TPK. Brute force they just drown the guys in spells and it's over.

Now, a combination of bad luck and stupidity should be able to turn almost any fight worth xp into a TPK: if the rolls all go bad and you run out of or refuse to spend your resources but keep fighting anyway then that's what you get, but that's only if both hit at the same time. Just bad luck or just stupidity should not result in a death for anything that's not a boss fight (and players tend to suddenly "learn kung fu" when a boss fight is looming). The monster's perfect round of attacks should never kill the fighter (who's job is to be in range-and don't' forget crits can happen), but it also shouldn't kill the wizard without a crit unless it's a boss. All of this gets harder to evaluate as save or dies start entering the picture, but that's part of the cleric's role: Death Ward and Freedom of Movement, for letting one or more people ignore those risks. Not having a cleric means a whole library of spells the game assumes you have for dealing with standard monsters, including those but also stuff like Remove Disease and Remove Curse, means that certain monsters become under-CR'd unless the PCs have good access to magic item replacements.

It sound be noted that the baseline rogue is not a frontliner, they are a squishy that can turn a battle when used properly. Sending the rogue in for a sneak attack is a risky move on par with burning a significant spell, so if the rogue and fighter together can win a fight that's okay-as long as the rogue is actually being threatened, with the same risk of death as the fighter even though they're likely spending less time in danger. It's a calculated risk that the rogue will land their attacks and speed up the fight enough to come out ahead, rather than flub an attack and take a ton of damage. The core rules assume the rogue is there mostly for trapfinding and scouting: If your party has more than one capable frontliner, then monsters need to be tough enough to survive long enough to possibly kill one of them before dropping regardless, and this may mean using tougher monsters or toughening up those you want to use. The same thing happens if the party has heavier spellcasting, as the monsters must have enough defenses that they can deal damage before failing their saves.

Optimized parties ignore the "skillmonkey" role by combining it with an extra frontliner or arcanist, and often combine the clerics "status removal/fallback fixer" role with frontliner or "arcanist." A well optimized party can be functioning at twice the capacity as the core game expects, allowing them to handle encounters one or two levels higher than normal without difficulty, but the DM must always remember that their actions, spell access, and maximum numbers are still limited. Some monsters are built with the assumption that no one under X level will fight them and efficiency can only do so much.

Obvious things to watch out for: foes that deal enough damage per hit that they can kill somebody in one or less rounds. Foes that rely on save or die/lose. Foes that rely on ambush tactics (including foes without threatening ranged options). Years of player agency train people to assume they go first, but initiative is a random roll and it's entirely possible to be out before you even take a turn. Foes that rely on save or lose are usually quite weak in combat and have to walk the line between scaring people with the saves but not actually hitting enough party members to win. Foes that rely on ambush are useless outside of an ambush, but because they are assumed to go first they cannot be allowed enough power to one-round someone, forcing you to handicap yourself.

And remember the "easy if handled properly" category, which are recommended as 20% of encounters. You don't actually have to try for these, as they'll occur naturally often enough when you put together a tough encounter that the players circumvent. Bruisers with no ranged attacks only work in enclosed spaces where the players have to fight them, but if the players can find a way to deal with them at range anyway then it's easy-because they handled it properly. Dragons have breath weapons that are quite nasty unless the party has been buffed with Mass Resist Energy-then they're a lot easier. A mob of threatening foes could be hard to deal with, unless you kept a fireball waiting. These are the encounters where your players get to feel like badasses because they have the right tool for the job, it's part of the game that's supposed to exist and that means it's okay to have tough encounters that don't have a checklist of every defense.