There are many instances in Pathfinder and other 3.5 based systems when you might need to reduce a monster below 1 or 1/2. For example, if I'm using a CR 1/2 monster from a 3.5 source in Pathfinder, I'm supposed to reduce it's CR by 1. So what do I do in this case? Reducing the CR by 1 using rote math would put me in negative territory. Or, for a more practical example, what if I want to include many weaker versions of a weak CR 1 enemy? I'd apply the CR -1 template, but then what would the CR be?

Do I drop down to the next fractional CR? Or do I go in halve the CR?

Note: I realize that this is partially a theorycraft question, since this situation only occurs at very low level encounters or in encounters with LOTS of low level enemies. However, it's been bugging me for awhile and I'd appreciate your input.


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    \$\begingroup\$ Welcome to RPG.SE. I'll be interested to see the answers people give to this question, as I imagine the idiosyncrasies of 3.5's CR system and monster-numbers-per-encounter rules are likely to break in interesting ways when converted to Pathfinder. \$\endgroup\$
    – GMJoe
    Apr 5, 2013 at 5:38
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    \$\begingroup\$ Welcome, this is a really good first question :o) \$\endgroup\$
    – Wibbs
    Apr 5, 2013 at 7:10
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    \$\begingroup\$ You can drop down to 1/3, 1/4, 1/6, and 1/8 CR, but the monster creation rules don't assume monsters that weak. I guess I would just use the fractional CR creatures as a guideline if I were coming up with my own. \$\endgroup\$
    – okeefe
    Apr 5, 2013 at 7:46
  • \$\begingroup\$ Wouldn't dropping a 3.5-CR1/2 monster by 1 CR put it at exactly PF-CR1/2? \$\endgroup\$
    – Eric
    Apr 5, 2013 at 11:35
  • \$\begingroup\$ Welcome to RPG.Stackexchange.com! Great first question! Please take a moment to look at the About page. \$\endgroup\$
    – C. Ross
    Apr 5, 2013 at 12:21

2 Answers 2


Lower them by steps, not value

I'd suggest working with what @okeefe has suggested; scale down the monsters in steps once they reach CR 1/2.

The steps being

CR: 2 -> 1 -> 1/2 -> 1/3 ->1/4 -> 1/6 -> 1/8

So a CR 1 monster reduced by 1 becomes CR 1/2

A CR 1/2 monster reduced by 1 becomes CR 1/3

With no further lowering below 1/8.

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    \$\begingroup\$ I really like your use of sup and sub to achieve skewed fractions. Very clever. \$\endgroup\$
    – KRyan
    Apr 5, 2013 at 13:01
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    \$\begingroup\$ They're also available as characters: ½ ⅓ ¼ ⅙ ⅛ \$\endgroup\$
    – okeefe
    Apr 5, 2013 at 15:46
  • \$\begingroup\$ Ah, I didn't know 1/6 and 1/8 were available as characters; that's useful to know. :) \$\endgroup\$
    – Rob
    Apr 5, 2013 at 15:48

The CR System Doesn’t Work

There’s not really any good answer to this, because the CR system of 3.x simply doesn’t work. To begin with, player power levels, at any given level, vary massively based on choices of class and feats, so it’s impossible, on the face of things, for monsters of that CR to be “appropriate” for all of them. This is equally true in Pathfinder as it is 3.5.

Furthermore, I have not spent any time reading Pathfinder’s monsters, but 3.5, at least, had some monsters that are ridiculously poorly-CRed. Dragons were under-CRed by tradition; while one expects a dragon to always be a difficult fight, an intelligently-played dragon could be almost impossible to kill at the “right” CR unless the player optimizes very hard. The Tarrasque, on the other hand, doesn’t really pose any significant threat to a 20th-level character, since it is dumb and cannot do things like fly, hit ethereal creatures, and so on.

Monster Manual II is probably the most notorious source of CRs being just wrong all over the place. The worst of the lot, the Adamantine Horror, gets things like disintegrate (6th-level spell) and disjunction (9th-level spell) at will. Apparently someone thought this would be appropriate for CR 9.

So basically, because the CR system doesn’t work, it doesn’t matter what you do, you will never come up with a consistent system between 3.5 and Pathfinder. It makes a lot more sense to try to estimate a creature’s actual threat level to your actual party, and base encounters and rewards on that.


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