CR?

[SlashRunner]

As a new DM, I'm having trouble having monsters challenge my players. This probably is because I don't understand the CR system extremely well. So, is CR supposed to represent the level of the GROUP that the monster should be able to hold it's own against or the level of the INDIVIDUALS in the group? So, would a good boss for a group of 3 3rd level characters be CR 4-5 or CR 9?

[Tvtyrant]

Its a monster that takes a percentile of resources from a group to defeat (supposedly 20%). So a CR 10 monster should be enough to take up 1/5 of the daily resources of a 4 person level 10 party.

At party of of level 3s should have a CR 4-5 boss, a CR 9 monster will likely kill them all.

[Rei_Jin]

In theory, Challenge Rating, or CR is supposed to represent the challenge that a single monster will present to a balanced group of characters. If you had the iconic four man party (Wizard, Cleric, Rogue, Fighter) and they were all level 3, then the CR System suggests that they could defeat a single CR 3 monster by expending 20% of their daily resources (Spell slots, Hitpoints, per day abilities, etc).

Further to that, each time you double the number of monsters in the combat, if they have the same CR, you add +2 to the CR. So, whilst one CR 3 critter is a fair challenge to your 3 man party, two of them is a CR 5 and is much more deadly.

Of course, this assumes that everything works as Wizards of the Coast designed it, and it never does.

[LOTRfan]

This (http://www.penpaperpixel.org/tools/d20encountercalculator.htm) might help, as well.

[tyckspoon]

CR is supposed to compare to the entire party. Specifically, an equal CR encounter is one that should, theoretically, somewhat drain but not really threaten a 4-character party such that the party can safely handle 4 such fights in a day, but would be risking death to do a 5th. CR +1 is supposed to be actually challenging, CR +2 is supposedly serious risk of death, and CR +3 or higher is probable TPK, party should be seeking a way to escape the combat/avoid starting a fight with this particular creature.

That's how it would work if the system math was sound and consistent, anyway. It's not, which means you're basically back to 'learn what your players can handle and eyeball it'. FWIW, for the party you describe CR 4 would be an appropriate boss, because they're short-handed by only being 3 characters.. although I'd probably construct it as a CR 3 'boss' with a couple of CR 1 or 2 minions to make up an EL 4 or 5 fight (EL is Encounter Level; it's what you get when you use multiple monsters. It's supposed to have basically the same function as CR, just for groups.)

[SlashRunner]

Doesn't a monster with class levels gain a CR equal to their character level? In which case a CR 4 boss would be equivalent to a 4th level character fighting 3 3rd level characters?

[KillianHawkeye]

Keep in mind that the CR system assumes you're using the same unoptimized group that WotC assumed would be the norm when they designed the system: meat-shield fighter, trapmonkey rogue, healbot cleric, and blaster sorc/wizard.

As such, it works okay for beginning players and not so well for people who really know what they're doing.

EDIT:

Doesn't a monster with class levels gain a CR equal to their character level? In which case a CR 4 boss would be equivalent to a 4th level character fighting 3 3rd level characters?

Yes, an NPC with PC class levels (a Fighter, for example) has a CR equal to its level. If it's a monster with class levels, then its CR is increased by its class levels or by half its class levels depending on whether or not the class is considered an "associated" class (meaning it plays to the monster's strengths).

[SlashRunner]

My group are all level 3, a Soulknife (who, despite the terrible class choice, is better than the other two combined), a Cleric (who knows nothing about the rules. He tries to convince me that he gets 2nd level spells upon leveling to 2nd level because "it makes sense" and attempts to cast spells as attacks of opportunity), and a rogue who is new to RPG's in general but is picking up the rules really fast. All of them are completely unoptimized (except for the Soulknife, but he isnt REALLY optimized, he just has planned his feat choice ahead a bit.)

[tyckspoon]

Doesn't a monster with class levels gain a CR equal to their character level? In which case a CR 4 boss would be equivalent to a 4th level character fighting 3 3rd level characters?

Officially, yes, but how close they come to actually fitting the mark depends very heavily on how you build them. A 4th level Fighter, for example, can either be a complete walkover, or he can potentially kill the party if they aren't careful or are the wrong builds (a 4th level sword-and-board setup, for example, will get stomped by action economy, while a 4th-level tripper with reach and Combat Reflexes could lock down an entire 3-man group if none of them have good ranged options. Or, really, compare how a 4th level Wizard can fight groups with how a 4th level melee has to do it.)

Edit: Yeah, ok, for that group you can probably go by CRs as listed and do alright.

[Douglas]

CR is supposed to compare to the entire party. Specifically, an equal CR encounter is one that should, theoretically, somewhat drain but not really threaten a 4-character party such that the party can safely handle 4 such fights in a day, but would be risking death to do a 5th. CR +1 is supposed to be actually challenging, CR +2 is supposedly serious risk of death, and CR +3 or higher is probable TPK, party should be seeking a way to escape the combat/avoid starting a fight with this particular creature.
On the high end, CR +4 is supposed to be an even match for a party of four characters - 50% chance of TPK if they fight to the death. CR +3 is a major threat, but not all that likely to TPK a standard party.

For a 3 member party you have to scale things down a little, though, and it also varies a lot depending on how optimized the PCs are.