Bruiser Monsters: How much is armor worth?

[Tvtyrant]

This is a basic question in relation to low cr bruisers. Elephants and Ogres are good examples; how much CR is armor worth? Like an Ogre in Plate with a Shield is clearly a rich Ogre in setting, but what are they worth points wise? What does Splint do to Elephant CR?

[Rukelnikov]

That's in the Dungeon Master's Workshop section of the DMG in the Create a Monster part (pg 273)

tl;dr: About 1 CR every 4 AC points

So in order to come up with the final CR of a monster you need to calculate its Offensive and Defensive CR

The defensive CR of a creture is based on its HP total, which gives us the "base CR" so to speak.

An elephant has 76 hp, thus we check the table and it suggests a base defensive CR of 1, now the table also tells us the expected AC for a creature of this defensive CR is 13, and we need to adjust it by 1 for every 2 points above or below this, so an AC of 11 would become a defensive CR 1/2 an AC of 15 would became a defensive CR of 2.

Since final CR is then the halfway point between defensive and offensive CR it means every 2 points of defensive CR will become 1 point of final CR, so

+4 AC = +2 Defensive CR = +1 CR

Of course there are cases where just bumping AC by 1 would increase its defensive and final CR, but as a rule of thumb +4 AC equals +1 CR

[quindraco]

This is a basic question in relation to low cr bruisers. Elephants and Ogres are good examples; how much CR is armor worth? Like an Ogre in Plate with a Shield is clearly a rich Ogre in setting, but what are they worth points wise? What does Splint do to Elephant CR?

The process is as follows:

1) You calculate the creature's equivalent HP - this is its real HP, modified upward by certain abilities which are "worth" various amounts of HP.
2) You look up the the HP in the table. Ignoring some strangeness below CR 1 and above CR 19, this is linear in HP - every 15 hit points is another CR step.
3) This HP value has an expected AC. You can convert CR to AC without a table lookup as follows: PCs are assumed to have an ability modifier to-hit of +3 from levels 1-3, +4 from 4-7, and 5+ from 8 to 20, and are assumed to attack with a weapon with which they are proficient, and should have a hit probability of 65%. So expected AC starts at 13 (hitting on 8s) and then proceeds as necessary to maintain hitting on 8s, so eventually it's AC 19 at level 17. The only exception to this is level 9, which "hiccups" and lets PCs hit on 7s, so the level 9 AC is 16, not the 17 you'd expect.
4) Find the converted AC value of the creature (like HP, this is real AC modified by some abilities) and compare it to expected AC. For every 2 points of difference up or down, move CR up or down 1. In other words, move CR up or down by half the difference in AC, rounded towards 0.
5) This calculates the monster's Defensive CR, or DCR. Offensive CR, or OCR, is calculated separately. When you're done, add OCR + DCR, divide by 2, and round to the nearest CR (this takes some work for the fractional CRs).

Note that many monsters do not have CR values matching the above, which is exacerbated by many having "incorrect" values, like how an allosaurus's Pounce DC is 1 lower than it should be, given how Pounce DCs are universally calculated (this makes allosauruses have the same DC as tigers, despite being stronger).

Ogres are very straightforward:
HP: 59 -> DCR 1/2
AC: 11 is 2 less than 13, so reduce DCR by 1, but the lowest legal CR is 0, not -1/2. So DCR 0.

OCR: DPR 13 is CR 1, adjusted to CR 2 for +6 to hit (this works like DCR, just with DPR instead of HP and hit bonus instead of AC; note that DPR raises CR every 6 points, and hit bonus simply doesn't follow any known algorithm).

Net CR: 1. Ogres are listed as CR 2, but their defensive statline (AC 11, due to hide armor) is so bad they should be listed at CR 1. Since DCR 1 or 1.5 would be sufficient to make them honestly CR 2, you could put an ogre in chain mail and make it proficient to make it just be AC 16, which would render it DCR 1.5 (expected is 13, and 16 is 3 more than that, half of which rounded down is 1, so raise DCR by 1) and net CR 2.

[Tvtyrant]

That's in the Dungeon Master's Workshop section of the DMG in the Create a Monster part (pg 273)

tl;dr: About 1 CR every 4 AC points

So in order to come up with the final CR of a monster you need to calculate its Offensive and Defensive CR

The defensive CR of a creture is based on its HP total, which gives us the "base CR" so to speak.

An elephant has 76 hp, thus we check the table and it suggests a base defensive CR of 1, now the table also tells us the expected AC for a creature of this defensive CR is 13, and we need to adjust it by 1 for every 2 points above or below this, so an AC of 11 would become a defensive CR 1/2 an AC of 15 would became a defensive CR of 2.

Since final CR is then the halfway point between defensive and offensive CR it means every 2 points of defensive CR will become 1 point of final CR, so

+4 AC = +2 Defensive CR = +1 CR

Of course there are cases where just bumping AC by 1 would increase its defensive and final CR, but as a rule of thumb +4 AC equals +1 CR


The process is as follows:

1) You calculate the creature's equivalent HP - this is its real HP, modified upward by certain abilities which are "worth" various amounts of HP.
2) You look up the the HP in the table. Ignoring some strangeness below CR 1 and above CR 19, this is linear in HP - every 15 hit points is another CR step.
3) This HP value has an expected AC. You can convert CR to AC without a table lookup as follows: PCs are assumed to have an ability modifier to-hit of +3 from levels 1-3, +4 from 4-7, and 5+ from 8 to 20, and are assumed to attack with a weapon with which they are proficient, and should have a hit probability of 65%. So expected AC starts at 13 (hitting on 8s) and then proceeds as necessary to maintain hitting on 8s, so eventually it's AC 19 at level 17. The only exception to this is level 9, which "hiccups" and lets PCs hit on 7s, so the level 9 AC is 16, not the 17 you'd expect.
4) Find the converted AC value of the creature (like HP, this is real AC modified by some abilities) and compare it to expected AC. For every 2 points of difference up or down, move CR up or down 1. In other words, move CR up or down by half the difference in AC, rounded towards 0.
5) This calculates the monster's Defensive CR, or DCR. Offensive CR, or OCR, is calculated separately. When you're done, add OCR + DCR, divide by 2, and round to the nearest CR (this takes some work for the fractional CRs).

Note that many monsters do not have CR values matching the above, which is exacerbated by many having "incorrect" values, like how an allosaurus's Pounce DC is 1 lower than it should be, given how Pounce DCs are universally calculated (this makes allosauruses have the same DC as tigers, despite being stronger).

Ogres are very straightforward:
HP: 59 -> DCR 1/2
AC: 11 is 2 less than 13, so reduce DCR by 1, but the lowest legal CR is 0, not -1/2. So DCR 0.

OCR: DPR 13 is CR 1, adjusted to CR 2 for +6 to hit (this works like DCR, just with DPR instead of HP and hit bonus instead of AC; note that DPR raises CR every 6 points, and hit bonus simply doesn't follow any known algorithm).

Net CR: 1. Ogres are listed as CR 2, but their defensive statline (AC 11, due to hide armor) is so bad they should be listed at CR 1. Since DCR 1 or 1.5 would be sufficient to make them honestly CR 2, you could put an ogre in chain mail and make it proficient to make it just be AC 16, which would render it DCR 1.5 (expected is 13, and 16 is 3 more than that, half of which rounded down is 1, so raise DCR by 1) and net CR 2.

Great thanks! I appreciate your helps :smallsmile: