Reducing CR?

[TresGeek]

There are rules for improving a monster by adding class levels or templates, but I haven't found anything about reducing a monster's challenge rating. I'm working with only the SRD right now as I don't have access to my books.

For example, lets say we have a monster with the following relevant statistics.

Hit Dice: 7d8+21 (52 hp)
Base Attack/Grapple: +5/+13
Attack: Slam +9 melee (1d8+4)
Full Attack: 2 Slams +9 melee (1d8+4)
Saves: Fort +5, Ref +5, Will +6
Skills: Climb +9, Disguise +13, Listen +8, Spot +8
Challenge Rating: 4
Advancement: 8-10 HD (Large); 11-21 HD (Huge)

So basically I want to create a younger, or less skilled, version of this creature to ensure that the party has a fair chance -- somewhere in the CR 3 range. Using the Encounter Calculator a CR4 monster is a "Very Difficult" encounter for a party of five 1st level characters with a 270 XP rating. A CR3 critter would still be "Very Difficult", but with a 180 XP rating. I think that sounds about right.

I figure I can just reduce it's hit points by a couple of hit dice, say down to around 30-35 hit points. BAB down by a couple of points, maybe down to +3. Same for saves and skills, down by 2 points each.

Does this sound about right for a 1st level party? Are there any guidelines for reducing a monster's CR somewhere that I've missed?

 

[frankthedm]

CR is an Art, not a science.

I'd worry more about two swings at 1d8+4 with first level charcters. A foe with a fat chunck of HP is far less of a massacre than a foe that has a large damage output.

 

[TresGeek]

I figured I would only do one single attack each round, being a "less experienced" creature, and maybe reduce the damage to 1d8+2 or just 1d8. Being first level characters most of them could be taken out of commission with a single hit! Also three out of the five charcters are arcane casters.

Of course there is a non-combat way to "defeat" this monster, but if the party doesn't consider that option I want it to at least be a fair fight.

 

[Starglim]

The Monster Manual or the SRD tell you what the creature's BAB, base saves and skill points should be for a particular type and number of HD. You left out Type which is also a relevant statistic for this exercise. Its other statistics won't change, by the rules, unless its Size or its ability scores change.

Your idea of removing one of its natural attacks at lower HD is reasonable. Its damage die and damage bonus are set by Size and STR, unless its appendage is actually less developed in form, therefore smaller or less damaging, at lesser Hit Dice (think of it, perhaps, as changing the type of weapon equivalent to the attack, as if the appendage it uses for its slam changed to be more like a club than a mace). This might be appropriate if the lesser CR version is a juvenile and not fully grown.

Determining how many Hit Dice to lose to drop it by one CR is, as stated, more art than science, but you could take a guess from the table that shows how CR increases as the creature gains Hit Dice. For example, if this is a Giant, it would gain a point of CR if it gained 4 Hit Dice so possibly it would drop a CR if it lost 3 or 4 hit dice, other things being equal. I'd guess, myself, that a 4HD version will probably work as CR 3.

 

[TresGeek]

Ah, thanks! I had missed the Adding Hit Dice table the first time I looked through the SRD. That's very helpful. It's an Aberration, so a +1 CR increase is a 4 HD increase. I'll try reducing it from 7 to 3 HD, calculating the new BAB (HD x 3/4 = 2.25), and reducing the saves and skills. I may also reduce the strength (currently 19) a bit to reduce the damage bonus, since I'd indeed like it to be a juvenial. A potential damage of 12 is just a bit too high, in my opinion, for a group of 1st level characters.

I realize it's not an exact science, but I just wanted to know if I was at least hitting in the ballpark. Thanks again for your help!

 

[Corsair]

A potential damage of 12 is just a bit too high, in my opinion, for a group of 1st level characters.

orcs with great axes are not common in your games I take it?

 

[Particle_Man]

In 3.5 the default orc uses a falchion now. They are cleverly disguised to *look* like greataxes (as per the picture) but are really falchions with the falchion stats.

 

[Staffan]

Ah, thanks! I had missed the Adding Hit Dice table the first time I looked through the SRD. That's very helpful. It's an Aberration, so a +1 CR increase is a 4 HD increase. I'll try reducing it from 7 to 3 HD, calculating the new BAB (HD x 3/4 = 2.25), and reducing the saves and skills. I may also reduce the strength (currently 19) a bit to reduce the damage bonus, since I'd indeed like it to be a juvenial. A potential damage of 12 is just a bit too high, in my opinion, for a group of 1st level characters.

I realize it's not an exact science, but I just wanted to know if I was at least hitting in the ballpark. Thanks again for your help!

Looking at the stats you posted, it looks like the creature is Large. You might want to consider reducing it to Medium (I'd halve the size modifiers listed in the MM though). This would reduce the damage to 1d6+2 (d6 for size decrease, and +2 for the -4 reduction in Strength).

 

[Corsair]

In 3.5 the default orc uses a falchion now. They are cleverly disguised to *look* like greataxes (as per the picture) but are really falchions with the falchion stats.

2d4+4= max 12 anyways. Regardless my point still stands. In general, CR at low levels is dicey.

 

[Staffan]

Remember, "losing 25%" could mean losing one character out of four.