Factors Affecting CR and EL

[Hussar]

Every so often, I see threads talking about how the CR system is broken or doesn't work, or is useless. Frequently, although not always, these threads have a common element - an inattention to elements which change the equation. Perhaps the poster ignores the fact that there are 3 PC's as opposed to 4, or the CR of a given creature is under or over estimated, things like that. To address this, I'd like to explore as many factors as I can that can skew the CR/EL system. To start off with, let's look at the PC's.

PC Elements that affect CR

• 1. Point buy. This is something that comes up regularly. The point value, even if you don't use point buy, of a PC has a huge effect on how powerful the PC is. As a rule of thumb, 10 points above or below 25 point buy is worth about one level. If you break down the math, and compare a 35 point value PC to a 25 point value PC, you generally find that the 35 point PC functions one level ahead in pretty much all mechanical areas - hp, attack bonus, number of spells (although this varies on odd and even levels), skills etc.
  
• 2. Number of PC's. This one is a bit of a no brainer of course, but it does need to be repeated. CR assumes 4 PC's. More or less is going to affect how difficult an encounter is. At a rough guestimate, 1 PC is worth about 3/4 of a level. Thus 5 PC's is a very strong 4 PC group, while 6 PC's is definitely worth a 1 level boost. It should be noted however, that the PC's individually aren't opperating any higher - their BAB, saves etc are not any better, thus it tends to make for glass jaw parties. If things go right, they obliterate enemies much higher CR than usual, but, if the baddie is much higher CR, the PC's may not be able to affect it at all. It is usually better to simply add more lower level critters than move up to a higher CR one. It balances better.
  
• 3. PC synergy. This is harder to evaluate. Some classes work together better with other classes. Adding a bard takes away some front end power, but makes the whole group stronger. Paired with classes that come with allies such as druids or conjurers, bards can be very powerful. Some classes, OTOH, don't really synergize well with others. Warmages, IMO, are a great blaster class, but, don't really do anything to help the rest of the party. Adding a Warmage isn't much different than adding a fighter - it's offensive capability, but not really a team player. (Note, these are generalizations and not meant as comprehensive truths)
  
• 4. Player Synergy. Again this is hard to evaluate but, some players have a great grasp of tactics and others don't. If you have a group of good tacticians, then they will likely be able to deal with encounters much better than a group that fights as individuals. To give an example, a few years back, I ran a campaign and everyone simply acted as an individual in combat. Faced with multiple enemies, they would spread out to face them one on one or two on one, each trying to out do the others, rather than focusing firepower and using tactics. They died a lot. My current group OTOH, uses lots of battlefield control spells, tanglefoot bags, reach weapons, and focuses firepower for maximum effect. We have been able to take on much larger opponents because of this.
  
• 5. Class choice. Not all classes are created equal. While I don't have any rule of thumb for judging this, it should be taken into consideration. If your party consists of a ranger, monk, truenamer and rogue, you are likely not as combat powerful as a party consisting of the base 4. A party which chooses classes on the weak end of the scale is likely a level down from the standard.

When I pick this up later, I'll start dealing with the DM's side of the equation. The DM can do all sorts of things which will change up the EL of an encounter.

 

[Arkhandus]

Kinda part of Point #4 and Point #5, but more like a Point #6 itself: Munchkinism and Newbism. Munchies might wreck an encounter that is otherwise challenging for a normal party; newbs may totally fail to overcome an encounter that's otherwise made to be merely challenging to an average party. :\

 

[FireLance]

Hi Hussar, that's a pretty good starting list. I would add the following items on the PC side:

1. PC Gear. PCs that are under-equipped for their level, or equipped with items that do not enhance their combat effectiveness, are going to have a harder time in fights. Conversely, PCs that have access to more expensive equipment, or particularly effective equipment (e.g. undead bane weapons in an adventure or campaign that features many undead foes), will have an easier time in fights.

2. Challenge-specific PC effectiveness. Some PCs will have an easier time defeating specific challenges, e.g. a ranger against his favored enemies, a 3rd or higher level paladin against an enemy with a fear attack, a cleric against undead, etc. Some PCs will have a harder time defeating other challenges, e.g. a paladin against a non-evil opponent, spellcasters against creatures with good spell resistance, lightly armored characters against heavy hitters, etc.

 

[Hussar]

Continuing on...

DM Elements

There are many, many things a DM can do to skew CR/EL.

• 1. Mistakes in mechanics. This is probably the number on cause for complaints. The DM has his carefully constructed encounter splatted in the first round because he made a mistake on how a spell worked. Or, conversely, had a TPK for the same reason. Part of the job of being a DM is having a decent grasp on mechanics. Sometimes that means trusting your players that they actually do know the mechanics. Sometimes that means pulling out the PHB or Spell Compendium. In any case, if an encounter that should have gone one way goes in an entirely different direction, take a look at the rulings you made. Frequently, minor mistakes in adjudication can have large consequences.
  
• 2. DM tactics. If you enjoy a tactical game, you might play your baddies in a certain way. That can easily turn a fairly standard encounter deadly. Conversely, if every monster stands still in the middle of the room and lets the party gang up on it, you're likely going to have a lot of disappointingly easy encounters. There's a fine line between the two. Going one way or the other too far leads to wonky results. While it's great to have hobgoblins performing shield walls and using tactics, perhaps its a bit much when black puddings do the same.
  
• 3. House rules. It has to be said that when you start changing baselines, CR/EL will be skewed. If you are running a low wealth game, then encounters get more difficult. If you allow all six of your PC's to be gestalts, that will change things as well. The specifics of a given campaign and the house rules that campaign operates under will have some effect. A great example of this is Action Points. AP's have a huge effect on games - allowing a low level PC to take a second attack can really change an encounter. Be aware of the house rules you have made and how they interact with combat.
  

Of course, there is one other factor that can mess with EL/CR calculations:

Mechanics

• 1. Poor CR estimation. 3e Ogre, I'm looking at you. Not all creatures at a given CR are created equal. Some are stronger than others. At some times, designers have made mistakes and a creature is miss CR'd. It happens. Dragons are notoriously under CR'd. Be aware of it, and try to adjust. CR is not a replacement for a Mark I eyeball.
  
• 2. CR calculated based on single abilities. This also happens. Some creatures are over CR'd because of a single powerful special ability. Ogre Mage is a good example of this. It's far too weak for it's CR, but, it's magical ability is too powerful for a lower CR. Dragon published an Ogre Mage Fighter 5 Kensai 3 - a CR 17 encounter with 131 hit points. If it was a spell caster, I'd understand, but, this is meant as a melee combatant. That's not a CR 17 encounter, that's a speed bump. But, because of the cone of cold ability, an Ogre Mage starts at CR 9. There are other creatures like this as well.
  
• 3. Scaling advanced creatures. Some creatures get a LOT more powerful when advanced. Much more than their CR might warrant. In the World's Largest Dungeon, there is an advanced Cockatrice at CR 6. It has a fort save for petrification in the mid 20's. Extremely deadly even for good fort save characters. Not all creatures scale the same.

I hope that people will find this helpful. What other factors can you identify when talking about CR/EL?

 

[Moggthegob]

On the DM side, I have seen alot of overestimation of Pcs, caused by past underestimation. I recall a certian instance where we were fighting something that had blasphemy as a spell like at i belive 8th level. We were toast as we were all good-aligned.

Also, templates, yes I am looking at you Spellwarped. Spellwarped turns an alreayd nasty creature into something that makes me cringe. In particular I am recalling a spellwapred digester set down in front of a group of 6 3rd level characters, the way the encounter was set up the digester got a suprise round, well that took out our damage dealer, the spellcater tried casting scorching ray, to the tune of the digester becoming even more powerful and killing the cleric in two turns before the spellcaser figured out what was happening and the rogue failed to kill it. Nasty stuff.

Also, using exotic templates in parties with sorcerors instead of wizards, wizards can identify whatthey are up against enoguh to prevent silly things like falling into the spellwarped creature trap. Sorcerors, lacking the int and the skill points has a much harder time of it.

 

[blargney the second]

Funny timing to start a thread like this - I was just talking with Erywin about this today! Here are a couple that have come up recently:
1) Environmental effects. Cold and heat hazards are simply brutal. One of the PCs in my campaign just flubbed Fort saves against hypothermia and altitude sickness, so he's exhausted until further notice. OUCH!
2) Use of terrain. Fighting a pair of harpies is not easy if they're outdoors and flying over the edge of a cliff. (Victims of their song move towards them.) Their effective Encounter Level was much higher than the 6 their CR 4s would indicate.

 

[gizmo33]

"System"? Here's the "system" as I understand it: guess at how tough the creature is, then guess at how significant the modifiers to the situation would be. Guess at your party strength and synergy. Then put it all together and guess at how far off you are. IMO this is probably the best system you can have for a game with an unlimited number of options for powers and circumstances.

I don't understand people that complain about this system. It's like complaining that your dice are broken because they keep falling off the table and you're having a hard time finding them. So I think this is an interesting/informative thread for people that already understand the CR system, but I'm not sure about the people that don't get it.

 

[Hussar]

Oh, I agree CR/EL is far more art than science. There are simply too many variables to come up with hard and fast rules. However, you can be aware of a number of the factors that can affect things beforehand and better guess/predict how an encounter will go.

 

[Doug McCrae]

Power creep. PCs created using all the splat books are a lot more powerful because they can choose the best options and benefit from the best feat/PrC/item synergies.

The monsters from the later books, MM3 and MM4, tend to be a *lot* more powerful for their CR than the equivalent creatures in the MM. I'd estimate a +2 CR difference.

 

[BiggusGeekus]

Hussar, you really hit it with tactics. One thing I've noticed adventures not using too much of is "crowd control" monsters. Hold, sleep, fear. Those kinds of things. Zap the guys with the low WILL save and beat the snot out of the PC spellcasters. Target the cleric and the wizard. However, this is not terribly fun.

Another issue is that D&D CR is based on combat. Lets take a troll and give him a level of expert. CR 7 or thereabouts, a little confusing because NPC levels count one less than PC levels, but let's call our troll CR 8. As a combat encounter, this is reasonably solid. Though why a DM would make a troll with all those skill points only to use him as cannon fodder is a mystery.

Now as a roleplay encounter things get weird. Let's say our troll has skill ranks in Perform (musical theater) and Knowledge (broadway hits). The troll will not hand over an item the PCs need for a quest until they help the troll put on a performance of The Music Man for the troll's true love. How exactly do we rate this encounter? What level is it appropriate for? As Hussar noted, what if the party is made up of four bards? What if the party has no bards at all? Do we let the PCs make a Perform skill check and call it a day? If they fail the skill check, how are they supposed to get the quest item without killing the troll? Because if they end up killing the troll, the DM may as well have made it a combat encounter.

A tricky thing to evaluate.