Post date: Sep 26, 2017 2:13:10 PM
I've realised that another factor screwing with me is D&D 5th's policy of having a lack of substantial improvement. Major upgrades are known to be unlocked at 5th, 11th and 17th levels. Outside of these major abilities, however, there's not a huge difference in power.
So, I'm going to take a look at a few different monsters: the CR 1 Brown Bear (BB), the CR 5 Barbed Devil (BD), the CR 11 Chain Devil (CD), the CR 17 Adult Red Dragon (AdR), the CR 24 Ancient Red Dragon (AnR), and the CR 30 Tarrasque (TR). I'll just be looking at base statistics here.
HP: BB has 34 HP. BD has 110. CD has 85. AdR has 256. AnR has 546. TR has 676.
I estimate PCs to have around 10 HP per level. HP scales with level. As shown with the CD, this can change to compensate for other abilities.
AC: BB has 11. BD has 15. CD has 16. AdR has 19. AnR has 22. TR has 25.
With PCs, AC doesn't typically scale with level, and is usually dependent on their equipment. I've found that my players' tanks tend to have 18-26 AC, and the squishies to have 11-14. The above seems like a reasonable guideline for determining a monster's AC, perhaps with a + or - 2 variation.
Attack: BB has +5, BD has +6, CD has +8, AdR has +14, AnR has +17, TR has +19.
The curve starts out slow, but ramps up quickly towards the higher levels, before slowing down again. I think a monster's to hit should also depend on how well they can avoid being locked down by a tank. A maneuverable monster can be threatening with lower attack, since they can choose to attack targets that are easy to hit. Again, I'll try to use the above as a guideline, with a +-2 variance.
Damage: BB deals 2d6+4, BD deals 2d6+3, CD deals 2d6+4, AdR dealso 2d6+8, AnR deals 2d6+10, TR deals 4d8+10.
There's surprisingly little variance here. Attacks seem to be more of a product of a creature's attributes, generally Strength.
Multiattack: BB has 2, BD has 3, CD has 2, AdR has 3, AnR has 3, TR has 5.
The number of attacks a monster has seems to be proportional to the number of strikers it has, allowing it to make one with each.
Based off the information from Attack, Damage and Multiattack, I can say that much of a creature's damage output comes from its abilities, rather than its attacks. The Tarrasque seems to be an exception, and seems more like what I'd class as a "Duelist"; it's relatively poor at dealing with multiple targets outside of focusing them down one at at time.
In conclusion:
HP is fairly flexible. I'd add in this value last of all when building a creature, as it can be used to compensate for any other values or abilities a creature might have.
AC should be rigid. I might + or - up to 2 points, but I'd use the other variables to give a creature toughness.
Attack. This seems to be roughly 1/3 or 1/2 of AC, but it should line up with a creature's attacks. I might add up to +3 if the creature uses magical weapons or something.
Damage. Basic attack damage sits well at 2d8. While creatures might be wielding a longsword (1d8), it's probably simpler to have them deal 2d8, rather than trying to buff their damage output elsewhere.
Multiattack. For monsters, three seems to be the right value after level 5, with abilities making up the rest of their threat. For NPC fighters, I think giving them one more attack than an equivalent level fighter would be a good rule, with abilities making up the rest of the threat.
Anyway, I'll use this information to help with my creature building in the future.