Help with calculating monster CR

[stenver]

Let us build an easy custom zombie

Atck +3 dmg 1d6+1 => Attack CR 1/4

Hp 21, damage immunities: Posion, Cold, Piercing. Damage resistances: Bludgeoing, magic weapons, fire

When calculating effective HP, is it
21 * 2(resistances) * 2(immunities) = 84
or just
21 * 2(resistances,immunities) = 42

Another question,

when calculating average CR and you have a tie, is it simply your choice wether to round up or down?
e.g.
Defence CR 1
Attack CR 2
Decide wether CR 1 or 2 on your gut feeling?

Thank you

[Giant2005]

The book doesn't say about the first question but I'd err on the side of caution and give it an effective 84 HP. Although my main reasoning for that judgement is the fact that the HP by CR listings on the table are so very, very wrong and scale a lot faster than they should. My ruling is essentially a bandaid on a very broken system. I'm pretty sure the HP table is using the creature's maximum HP as a metric when it is the creature's average HP which we use in play. The math of 21 HP doesn't work in the system, so I can't really reverse engineer that number but 22 HP is possible (4D8 HD) which would be a max of 40 HP which is the figure that the table seems to be using rather than the final result (In the Zombies case, it would be that 40 HP that was doubled, tripled or quadrupled depending on how you rule the resistances and immunities stacking).

As for the second question, 0.5 rounds up, so the average of 1 and 2 is 2. They even have an example of 2 and 3 averaging to 3.

[pwykersotz]

I'm gonna disagree completely with Giant2005 on this one. If the immunities are expected to affect combat (Cold and Piercing both are pretty hefty), double it once. Don't stack the multipliers from immunities, or from resistances. Use the highest one only.

He is completely correct on the CR though, round up when determining CR.

Giant2005, I am incredibly curious how you think the HP has scaled too fast. I've made lots of custom creatures and I've never gotten that impression. I think the guidelines are pretty solid. And it definitely means "average" HP, not max.

[Giant2005]

Giant2005, I am incredibly curious how you think the HP has scaled too fast. I've made lots of custom creatures and I've never gotten that impression. I think the guidelines are pretty solid. And it definitely means "average" HP, not max.

None of the HP limits for each CR even come close to matching anything in the books. The highest HP creature of every CR has considerably less HP than the values in the table and often, the highest HP creature of any given CR has considerably less HP than the minimum threshold for that CR in the table.
I know the average HP are supposed to be used, but the numbers are incredibly borked while doing so - they actually come far closer to the critters in the Monster Manual if we input the maximum HP rather than the average (And then use the actual average in play).

[pwykersotz]

None of the HP limits for each CR even come close to matching anything in the books. The highest HP creature of every CR has considerably less HP than the values in the table and often, the highest HP creature of any given CR has considerably less HP than the minimum threshold for that CR in the table.
I know the average HP are supposed to be used, but the numbers are incredibly borked while doing so - they actually come far closer to the critters in the Monster Manual if we input the maximum HP rather than the average (And then use the actual average in play).

I'm afb for tonight. Are you sure you compared it with special ability multipliers and offensive CR? I'll check tomorrow and see if I come to the same conclusion.

[Giant2005]

I'm afb for tonight. Are you sure you compared it with special ability multipliers and offensive CR? I'll check tomorrow and see if I come to the same conclusion.

No I didn't compare individually with offensive CR and resistances/immunities. I used this (http://www.giantitp.com/forums/showthread.php?387385-Monster-Stat-By-CR-(58-Done)) to compare with the table. That resource lists the highest, lowest and average HP for each CR and all of them fall short of the table (And in multiple cases the creature with the highest HP of a CR level has less HP than the minimum threshold of HP for that CR). So either every monster in the MM has a lower defensive CR that is balanced out by a higher offensive CR (Which is possible but unlikely), or the table in the DMG doesn't reflect what we are given in the MM. By using that table, with the average HP, you get lower defensive CRs than the creatures in the MM which results in a vcreature with a lower average CR than usual.

[stenver]

The MM monsters have stuff that multiplies their effective CR. Coupled with those multipliers, the HP of the table is pretty correct

[Giant2005]

The MM monsters have stuff that multiplies their effective CR. Coupled with those multipliers, the HP of the table is pretty correct

But it isn't. Choose any creature purely at random and you can easily see your statement is untrue.
Take the Grick for example, it inflicts 14 damage per round, with a +4 to hit. That gives it an offensive CR of 1.
Defensively, it has 27 HP which are an effective 54 due to its damage resistances, and an AC of 14. That gives it a defensive CR of 1/2.
Averaging those out, you come up with what would be a CR 3/4 creature but rounds to CR 1.
Yet in the book, the Grick is a CR 2 creature.

Or the Gnoll Fang of Yeenoghu, it inflicts 20 damage per round, with a +5 to hit. That gives it an offensive CR of 3.
Defensively, it has 65 HP and an AC of 14. That gives it a defensive CR of 1/2.
Averaging those out, you come up with what would be a CR 1 3/4 creature but rounds to CR 2.
Yet in the book, the Gnoll Fang of Yeenoghu is a CR 4 creature.


Those are just two critters in the book that were almost randomly chosen (I say almost because the first couple of pages I went to had complicated monsters with funky abilities like spellcasting that complicated things). It is pretty easy to see that it is the defensive CR that is really screwing them over unnecessarily - something with 65 HP and 14 AC shouldn't have a defensive CR that absurdly low - 65 HP is literally over double the HP of the CR 1/4 monster in the book with highest HP.

[GiantOctopodes]

No I didn't compare individually with offensive CR and resistances/immunities. I used this (http://www.giantitp.com/forums/showthread.php?387385-Monster-Stat-By-CR-(58-Done)) to compare with the table. That resource lists the highest, lowest and average HP for each CR and all of them fall short of the table (And in multiple cases the creature with the highest HP of a CR level has less HP than the minimum threshold of HP for that CR). So either every monster in the MM has a lower defensive CR that is balanced out by a higher offensive CR (Which is possible but unlikely), or the table in the DMG doesn't reflect what we are given in the MM. By using that table, with the average HP, you get lower defensive CRs than the creatures in the MM which results in a vcreature with a lower average CR than usual.

I'll use the Green Dragon Wyrmling as an example, since I was just looking at that very thing a little while ago. They're CR2, which means they should have 86-100 HP, instead they have 38, which puts them at CR1/4. Seems to support your hypothesis. However, it's an incomplete picture. One, they're immune to poison, and since their CR is 1-4, that doubles their EHP, so they're actually at 76. That would be a CR of 1, but only with an AC of 13. Their actual AC is 17, so being 4 higher, raises their defensive CR by 2. As such, their defensive CR is 3. Their offensive CR is also 3, with 20 expected damage per round, but the fact their final CR is 2 shows they didn't blindly stick to the table. With only 38 base HP, they apparently felt it was appropriate to assign it a Lower CR than its defensive abilities would indicate.

My point being don't forget to take immunities, AC, and other things into effect when looking at that. It is indeed incredibly rare that a creature is just a big old easy to hit HP sponge, instead being way more common to have very high ACs even at low total CRs, and for them to have much higher offensive CRs balancing out lower defensive CRs, so I'm not disagreeing with your overall assessment of the weird design of monsters in this edition, just pointing out there's more to it than meets the eye.

[Giant2005]

I'll use the Green Dragon Wyrmling as an example, since I was just looking at that very thing a little while ago. They're CR2, which means they should have 86-100 HP, instead they have 38, which puts them at CR1/4. Seems to support your hypothesis. However, it's an incomplete picture. One, they're immune to poison, and since their CR is 1-4, that doubles their EHP, so they're actually at 76. That would be a CR of 1, but only with an AC of 13. Their actual AC is 17, so being 4 higher, raises their defensive CR by 2. As such, their defensive CR is 3. Their offensive CR is also 3, with 20 expected damage per round, but the fact their final CR is 2 shows they didn't blindly stick to the table. With only 38 base HP, they apparently felt it was appropriate to assign it a Lower CR than its defensive abilities would indicate.

My point being don't forget to take immunities, AC, and other things into effect when looking at that. It is indeed incredibly rare that a creature is just a big old easy to hit HP sponge, instead being way more common to have very high ACs even at low total CRs, and for them to have much higher offensive CRs balancing out lower defensive CRs, so I'm not disagreeing with your overall assessment of the weird design of monsters in this edition, just pointing out there's more to it than meets the eye.

You don't double the effective HP for a single, rarely relevant Immunity. The Green Dragon Wymling has a defensive CR of 1/4 which is shifted to 1 via their 4 point AC increase. The offensive CR is 2 (You average the damage for 3 rounds when a limited use damage is an option and double the damage of an AOE attack to assume it hits two targets: (21*2+7+7)/3 = 18.67 damage per round). Using their system, the Green Dragon Wyrmling is supposed to be CR 2 and is one of the rare cases that actually meets that target - although very barely. Its HP only makes it into the CR 1/4 mark by a paltry 3 HP and even then it relies on generous rounding (rounding 1.5 up to 2) in order to reach its CR.

[GiantOctopodes]

You don't double the effective HP for a single, rarely relevant Immunity. The Green Dragon Wymling has a defensive CR of 1/4 which is shifted to 1 via their 4 point AC increase. The offensive CR is 2 (You average the damage for 3 rounds when a limited use damage is an option and double the damage of an AOE attack to assume it hits two targets: (21*2+7+7)/3 = 18.67 damage per round). Using their system, the Green Dragon Wyrmling is supposed to be CR 2 and is one of the rare cases that actually meets that target - in this case mainly because of its high AC and the fact that 1.5 rounds up to 2.

Poison is hardly rarely relevant, for Rogues and Rangers alike, all martials in fact, it is the most common non-physical damage type. I agree that their example is in such a way that it is possible to interpret it where you would only ever apply the multiplier if they have resistance to non-magical weapons, but that is not the way I interpret that part of the text. On Offensive, I'm well aware, but you missed the poison damage for its most effective combat options, it's ((21*2)+(7+3)+(7+3))/3) = 20.66 damage per round. However I did miss that you round down explicitly in the average damage calculation, and not to the nearest, so it would still round down to 20, the very top for CR 2 but CR 2 nonetheless.

[JNAProductions]

I've never had a player use poison damage. It's not really that relevant, at least in my experience.