By Sarah L. Stewart
Continued from NPC Stat Blocks for Frostlands of Fenrilik Part 1
Calculating Challenge Rating
Now, finally, I reached the hard and annoying part: running everything against the table in the DMG to calculate a Challenge Rating and make any needed adjustments.
The table is weird. For simple monsters / NPCs you pick a CR for the creature and then go across for their stats. Here’s what it looks like from CR 4-8, the range I expected my NPC stat block to fall in:
| CR | Proficiency Bonus | Armor Class | Hit Points range | Attack Bonus | Damage / Round | Save DC |
| 4 | +2 | 14 | 116–130 | +5 | 27–32 | 14 |
| 5 | +3 | 15 | 131–145 | +6 | 33–38 | 15 |
| 6 | +3 | 15 | 146–160 | +6 | 39–44 | 15 |
| 7 | +3 | 15 | 161–175 | +6 | 45–50 | 15 |
| 8 | +3 | 16 | 176–190 | +7 | 51–56 | 16 |
The second and third values (Armor Class and Hit Points) determine the creature’s Defensive Challenge Rating. The Attack Bonus and Damage (or Save DC for spell casters) set the creature’s Offensive Challenge Rating. The Creature’s CR is the average of the two.
Based on what I’d done so far, my custom ranger NPC stat block’s results were:
- Proficiency Bonus +3 (for being 7th level, although this can change if the CR changes) = CR 5-8
- AC 14 (with leather armor) = CR 4
- 7d8+7 Hit Dice (which is 5.5 * 7 = 38.5 Hit Points) = CR 1/4
- This is way too low for my target range, but I expected that. I almost always add more Hit Dice when creating custom creatures or NPCs.
- +6 Attack Bonus (with the +3 Dexterity modifier) = CR 5-7
- Save DC 13 = CR 0-3
- That’s much lower than my target, but they’re not primarily a caster. I’m going to focus on their damage, not their Save DC, to calculate their Offensive CR.
Calculating the average damage takes a little more work. I gave the character two shortswords, light weapons for two-weapon fighting. They have three attacks per round from two-weapon fighting and an extra attack (that technically requires using a bonus action, but I’m simplifying things, and NPCs and monsters frequently get extra attacks anyway to bump up their damage). As I previously described, once per round they get extra damage due to their archetype. Finally, there’s extra damage if they cast hunter’s mark. In total the average per round is:
- Weapon damage: 3 (d6 +3) = 19
- Archetype power: 1d8 cold damage = 4
- Concentration spell: 3d6 for hunter’s mark (cast at the maximum available level) = 10
This is a total average damage of 33, which is a CR 5.
So my Defensive CR values at this point were 4 (armor class) and 1/4 (hit dice), and Offensive CR values were 5 (attack bonus) and 5 (damage). It would be easiest to make this character class a CR 5. That’s on the low end of what I wanted, but acceptable. And, more importantly, I wouldn’t have to change the proficiency bonus from my original build (both CR 5 and ranger level 7 have a +3 proficiency).
Things to Look out for When Calculating CR
- Remember, when you’re tweaking things to reach a specific CR, redo your math for the Attack Bonus and Save DC if you change either proficiency bonuses or stats. This is really, really easy to forget.
- If any of your OCR and DCR values are less than CR 1, you can’t simply calculate the average of the values. See the DMG for specific instructions on how to use the table when that happens.
- The AC column doesn’t go above 19. If your creation’s AC is higher than 19, check the equivalent value in the Save DC column to determine the AC CR (at least that’s what I do).
I needed to bump up the Defensive CR to reach my target. I could have added hit dice to get over 145 hit points — the CR 6 would balance the CR 4 for the armor class. Instead, I upgraded the armor to studded leather, bringing the class’s AC up into CR 5-7 range.
I did still need to add more hit dice. Rangers have a d10 hit die, but NPCs have a d8, so I used that. This class has a Constitution of 12, adding +1 per hit die. That equates to 5.5 hit points per hit die. I divided 131 (the bottom of the Hit Points range) by 5.5 and rounded up to determine the Hit Points. That’s 24d8 + 24, for 132 Hit Points.
Resistance and Immunities Check
One last thing to check. If my character had any resistances or immunities, that might impact their “effective hit dice.” I frequently forget this step when making NPCs, as while it’s very common for monsters to have resistances or immunities, it’s pretty rare for NPCs.
And indeed, my NPC did have innate protection versus cold (not at all surprising for the icy lands of Fenrilik). But this rule modifier only applies to those with more than one resistance or immunity (very common with monsters that have resistance to all non-magical weapon damage types). If my NPC had more than one trait, I’d be reducing their hit dice, but they didn’t, so I was all set.
Check and Check Again
If it sounds like it’s easy for errors to sneak into this process, you’re right — it is! My final step was to double-check all my language, punctuation, formatting, etc. Abilities have to be in alphabetically order, for example, which means that spells are not always listed at the end.
I highly recommend having an editor or friend familiar with 5e rules to check your work at this point. One of the great things about Fenrilik was having a whole team working together to review each other’s work. We collectively caught several little things and adjusted others to work better. Having fresh eyes on your work is a tremendous help.
If you want to see the final version of this ranger NPC stat block and a bunch of other cool content (excuse the pun) check out Frostlands of Fenrilik, available soon on DriveThruRPG in the Slarecian Vault https://www.drivethrurpg.com/cc/19/Slarecian-Vault.