D&D 3E/3.5 Scaling 3.5 adventures

[Oryan77]

I'd like to run the Forge of Fury adventure, but for a party of 10th level PCs. I just like the layout of the maps, and I plan to use completely different monsters & NPCs.

Is this an ok method of determining what CRs to use when I scale an adventure up:

1. I use an online encounter calculator and make note of the "% of this ESL to use" for each CR of monster/NPC that appears in Forge of Fury against a 3rd level party.

2. Then I plug in higher level CRs vs a 10th level party on the encounter calculator until I get a CR that shows the same "% of this ESL to use" as it did with the 3rd level party.

So for example, a CR 5 vs a party of four 3rd level PCs shows a 36% "% of this ESL to use". When I change it to a CR 12 vs a party of four 10th level PCs, it shows a 36% "% of this ESL to use".

Can I assume that I am scaling everything appropriately, or are there other factors figured in when creating adventures from scratch?

 

[Jhaelen]

Can I assume that I am scaling everything appropriately, or are there other factors figured in when creating adventures from scratch?

You can do it like that but is there any particular reason why you don't simply increase every EL by 7?

 

[FEADIN]

You can do it like that but is there any particular reason why you don't simply increase every EL by 7?

Yes, sometimes the EL is higher than the combined CR, it depends on tactics and terrain feature, beware!!!!

 

[HoboGod]

Well, if you're going from a level 3 game to a level 10 game, it makes sense to roughly triple (x3.33) the EL of each encounter. I understand it's hard to guesstimate on the fly what CR equals what EL, but yeah, an encounter calculator can be useful until you get a feeling for it.

 

[Herzog]

Maybe not particularly useful to you since you already plan to use completely different NPC's etc., but anway:

As a general rule, I scale encounters by increasing the number of monsters as long as the number of monsters is below the number of characters, and only start using higher CR monsters once/if the number of monsters is larger than the size of the PC group.

This is especially the case when your PC group is of a higher average level because you have 5+ PC's in the group.

 

[Oryan77]

You can do it like that but is there any particular reason why you don't simply increase every EL by 7?

Well I wasn't sure if it would still be balanced the same because when I fill out the encounter calculator with four level 3 PCs vs one level 2 NPC, it says that it is an "easy" encounter. But if I set it at four level 10 PCs vs one level 9 NPC, it says that it is a "challenging" encounter.

So even though it is 7 CRs higher and the % of this ESL to use is the same, the difficulty alert is different. It only seems to be different when the CR of the NPC is lower than the ECL of the party. When the CR of the NPC is higher than the ECL of the party, the difficulty alert seems to stay the same.

 

[Jhaelen]

Well I wasn't sure if it would still be balanced the same because when I fill out the encounter calculator with four level 3 PCs vs one level 2 NPC, it says that it is an "easy" encounter. But if I set it at four level 10 PCs vs one level 9 NPC, it says that it is a "challenging" encounter.

Grr, this has been the first time in ages I've lost a post

Anyway, here's the short version of my findings:
The calculator uses the chi/rho method of dividing the sum of the squared CRs by the sum of the squared pc levels to calculate the difficulty percentage:
(2*2/4*3*3) = 4/36 ~ 11%
vs.
(9*9/4*10*10) = 81/400 ~ 20%

This method is derived from the xp by level chart in the DMG. I.e. what it _really_ does, is measure the advancement rate, i.e. it makes sure you require the same number of encounters to reach the next level:
(100xp/3000xp) = 30 encounters to level up
vs.
(608/10000xp) ~ 16.5 encounters to level up

I still think it's a bit odd, but apparently that's the most accurate method to calculate difficulty.