View Full Version : Challenge Rating and encounters

09-21-2010, 10:01 PM
I don't understand creating encounters at all. Like, I want to design some monster encounters for a group of level 1s mostly, but there are six of them, and CR seems to be made for a party of 4. The DM guide states that this is addressed by giving the party of fewer more exp, but it doesn't really address making challenges tougher. I want to say multiplying the number of monsters by 1.5 (6/4) but then CR doesn't seem to work that way. Furthermore what's the equation for EL vs. CR? I saw on another forum someone say "4 CR 4 creatures, 3 CR 3 creatures and 1 CR 5 creature which adds up to about a 9.83 EL overall." and I can't for the life of me discover how that math works. But I'd love to have encounters with creatures of different CRs so I'd like to learn it..

I just looked at 4E for the first time and the system they use for encounters (more exp for greater challenge? Use exp for CR. Done) seems a lot better, and I'm sort of wondering if someone has already come up with a similar method adapted for 3.5e.

Sorry if none of this makes sense. Also is this the wrong place to write this I feel like it might be.

09-22-2010, 03:07 AM
Let's see if I remember this properly:

CRs (and ELs) are based on a party of four characters of the same level.
Challenge Rating is what applies to a single challenge/creature (and is used for determining XP).
Encounter Level does not determine XP, it's just the number you calculate to find out how hard the PCs will have to work.

The idea behind CR goes like this: the party (of four same-level characters) should have a level (whatever the same-level is) equal to the CR of a creature that will tax about 1/4 to 1/3 of the party's resources (hit points, spells, etc.). For example, a Lvl 4 party (four 4th level characters) will use up about a quarter of its resources on a CR 4 monster.

Now if you have several monsters, you combine their CRs to get a single number (EL) that you can compare to the party level.

The simple way to find EL is this: two creatures of the same CR are an EL two points higher than that CR. Example: two ogres (CR 2) are an EL of 4 (CR + 2). Just apply this rule to lump multiple creatures, and CRs, together until you have your EL.

1st exception: CR 1 or lower creatures. Two 1/8 CR creatures are not EL 2.125. You can generally add low CRs together until they equal one. Then use the CR+2 rule.

So, let's say, your party is level 5. For your encounter, you have a FTR 1, BRB 2, ROG 3, Giant Eagle 4, and Elemental 5 (and other problems besides calculating CRs). To find if these baddies are a decent challenge, do this:

- Combine the FTR and BRB into a CR 3 (for calculation purposes only). If two BRB 2s are a CR 4, then a 1 and a 2are pretty close to 3.

- Combine your new CR 3 with the ROG 3, for a CR of 5. (CR+2 rule)

- Combine your new CR 5 with the Elemental 5, for a CR of 7.

- Now you have a CR 7 and a CR 4. The 4 isn't near a 7, so you can't consider this with the CR+2 rule. Further, your CR 7 is really just the sum of lower CRs, so they're not as likely to pack as much punch as a natural CR 7. But adding anything to an encounter makes it more difficult, so your EL should be a minimum of 7 if you're adding the CR 4 to the CR 7. You can go on to look at the magic items and special abilities of all involved, but I would just consider CR 7 + CR 4 to be EL 8 and be done with it.

EL 8 is technically overpowering for a Party Level 5, so you might want to lighten the load of the encounter. Or, if your FTR and BRB are sissies (and are already low-level), you could the assume that the encounter will give the party a decent run for its money.

Regarding mixed parties/parties of numbers different than 4 (5 is right-out), use the Beat Up Rule. Four Lvl 1 PCs would have a party level of one. Can 6 Lvl 1 PCs beat up a party of four Lvl 2 PCs? Probably. Go ahead and consider your party level 2. Could they beat up a party of Lvl 3s? Probably not.

09-22-2010, 11:05 AM
Thank you, that actually helps a lot. I never thought to chain the math like that, but once you mention it things make a lot of sense.

The beat up rule is a really nice one too, though I can't really consider it until I have more experience (right now, would a team of six level ones be able to hold there own against a team of four level twos? I know they can because you just told me, but I haven't run through enough battles to really see it in action.)

09-22-2010, 02:09 PM
Don't forget to apply the appropriate DMG charts whenever possible. Glad to help.