CR Calculation methods

[Legoman]

Hey there,

I'm going to start DMing a campaign soon, and the players are all far more experienced in D&D than I could reasonably hope to become. I have a grasp of the rules, but the content, such as monsters and lore, is slightly beyond me.

The solution, then, is to simply create new content that keeps it entertaining for the both of us.

In order to do that, I'd need any advice possible on calculating the CR of created monsters. HD, SR, DR, abilities, the works. I'm looking at Vorpal Tribble here, as he seems to come up with good CRs for all of his creations, and It'd be nice to have that sort of mathematical precision.

Much thanks in advance.

[The Demented One]

I personally stat something up, aiming for a target CR range, and then compare it to similar monsters within that range. For example, if I mad a heavy damage dealer monster within a CR range of 9-12, I'd compare it's hp, AC, attack bonus, damage, DR, SR, and similar traits to creatures like Vrocks, Elder Earth Elementals, and Fire Giants. Remarkably effective way of doing things.

[Fualkner Asiniti]

I agree with D1, the only way to CR a monster is to compare it with others. unless your monster is unbliveibly powerful, ex. takes on 8 balor and wins without losing a quarter of its health. if you post the stats of your monster, I could help you with this.

[Fax Celestis]

A good rule of thumb: A creature's BAB should be about 3/4 it's CR, if you build creatures according to the MM guidelines. Conversely, you could go with the right column on page 302 of the MM and check that.

There, they say that CR should be different per creature type (and it should). For melee combat monsters, CR = 1/3 to 2/3 HD. Sneakier combat monsters, CR = 1/2 to HD. Magic casters, CR = HD to HD+2. Anything that combines the above effectively should be CR = 3/4 HD to HD+2.

Unfortunately, those don't really narrow it down. I find my rule-of-thumb to be rather appropriate: A CR 12 combat monster should have a BAB +9, because after Str mods, equip mods, and racial bonuses, its chances to hit the party will be about right.

[Legoman]

Alright, here's my first full fledged monster creation I drew up last night. The party will be fighting two of these in a room where jumping and climbing will be of the *utmost* importance.

Training Construct
Medium Humanoid Construct
3d10 HD (35 HP) (+20 Medium Construct Bonus)
Initiative: +3
Armor Class: 16 (10 +3 Dex +3 Natural)
DR: 3/--
Attack: Claw +7 (2d6+4)
Full Attack: Claw +7 (2d6+4)
[Alternative configuration is ranged;
Attack: Bolt +6 (1d8)
Full Attack: 2 Bolts +4/+4 (1d8)
*Creature must take a full round action every 5 bolts to reload.]
Fortitude: +3
Reflex: +6
Will: +3
Skills: Climb +12, Jump +12
Abilities: STR 18, DEX 16, CON -, INT -, WIS 10, CHA 1
Feats: Athletic
CR: 3