As Saga says, sometimes monsters just have arbitrary numbers because it ended up being what suited them best. This is particularly true when they have equipment that has no direct counterpart in PC equipment.
Source?
The Monster Manual
And yet... I see no link? I see no quote? Liar liar pants on fire. :)
As Saga says, sometimes monsters just have arbitrary numbers because it ended up being what suited them best. This is particularly true when they have equipment that has no direct counterpart in PC equipment.
Source?
The Monster Manual
And yet... I see no link? I see no quote? Liar liar pants on fire. :)
Says the person who has ignored the entire thread giving you examples of Monsters where Dex wasn't IN the AC calculation.
Hint - wanna know why there is no page reference for you there CC? The whole damn book is FULL of Monsters that break you opposed rule that you found that is wishy washy at best in being a true rule.
But the math gets easier if there's a -1 AC from Dex in there. The Dreadnoughts AC is X base + Y plate +Z1 shield + Z2 shield + Dex = 21. That's all I know for sure. If X is 10 as usual, 10+Y+2Z-1=21, or Y+2Z=12, suggesting Y=8 and Z=2. 10+8+2+2-1=21. So every time the giant drops a shield, -2 AC.
Nice!
This violates the rule in the PHB that shields don't stack, and violates the Fire Giant entry in the Monster Manual, in which Fire Giants are AC 18 with Dex 9 while wearing plate. Said entry is proof by itself that Fire Giants in Plate with Dex modifier -1 are AC 18 base, not 17. On top of that, those Fireshields aren't dealing Improvised Weapon damage, which must mean they have a special rule governing that - most likely that they count as one-handed melee weapons. On the other hand, their only benefit from the second shield must be additional AC, or they wouldn't carry a second one. The most plausible set of ACs for the Giant, with 2/1/0 shields equipped, is 21/20/18 - you only need to assume the Giant's shields count as melee weapons and it has the top line from the Dual Wielder feat.
Note also the MTOF entries for Tortles and Tortle druids completely neglect to point out that Tortle AC won't go up with a higher Dexterity bonus. It's extremely normal for Monster entries to leave out vital details for calculating stuff like AC on the fly. We can reasonably conclude from all of the Giants entries - especially Storm Giant Quintessents - that all of these Giants are AC 10 + Dex + Natural Armor base, and then follow the usual armor rules (see Storm Giants, both flavors, and the Fire Giant base flavor for evidence).
As for OP: there's no way to know for certain whether the Patchwork Armor is functionally +1 Half Plate or +1 Ring Mail, because on a DexMod -1 wearer, they have the same AC. However, Frost Giant Everlasting Ones have the same AC, the same armor, the same DEX, everything - except they can Barbarian Rage only better, and Barbarian Rage doesn't work in Heavy Armor. I would therefore conclude Patchwork Armor is functionally +1 Half Plate, although I would not conclude it is necessarily magical. This also means their base AC is 9, of course. Note that D&D 5E armor never provides an AC bonus - it provides a distinct way to calculate your AC. You can rule any way you like on the armor, but my recommendation is as follows:
It's perfectly normal Half Plate, but per the Frost Giant description of making their armor from enemy hides and gear, it's made from the scales of White Dragons they've been hunting (even base Frost Giants can easily demolish a Young or Wyrmling White Dragon). Unlike Dragon Scale Mail, this confers no benefits beyond functioning like +1 armor, but also doesn't count as magical in any way.
Storm Giants, Frost Giants, and, by way of an example, Knights (the humanoid kind, in plate) don't explicitly tell you that they have disadvantage on Stealth checks with their armor on, so just assume they all do.
With very few exceptions, you should generally assume Monster block entries assume all relevant proficiencies, which also applies here - just assume Frost Giants are proficient in Light and Medium armor.
As Saga says, sometimes monsters just have arbitrary numbers because it ended up being what suited them best. This is particularly true when they have equipment that has no direct counterpart in PC equipment.
Source?
The Monster Manual
And yet... I see no link? I see no quote? Liar liar pants on fire. :)
Maybe you missed it because it was on the last page, but I provided you a link.
Look, we have basically three options presented so far:
Option 1 (Chicken_Champ): Monster armor is always Dex+(some number or numbers representing armor in parenthesis).
Source: MM introduction, Armor Class: "A monster that wears armor or carries a shield has an Armor Class (AC) that takes its armor, shield, and Dexterity into account. Otherwise, a monster’s AC is based on its Dexterity modifier and natural armor, if any. If a monster has natural armor, wears armor, or carries a shield, this is noted in parentheses after its AC value."
Examples of monsters it doesn't work for? Zero. I could care less that "plate" means a different number on different monsters, doesn't hurt my position one bit.
How hard is it to use in play? "This monster has an AC 15 with natural armor. It just received +2 Dexterity, so now its AC is 16."
Option 2 (Doug_Booshaka, Quindraco, Lyxen, some of Saga's posts but not others): Monster armor is similar to player armor, so "heavy armor" ignores Dex, while "medium armor" might cap Dex bonus to a certain amount, and we should look to the PHB player armors for same/similar named armors to figure out if armor is light, medium, or heavy.
Source: No source.
Examples of monsters it doesn't work for? Countless. The fact that Plate results in a different calculation for Fire Giant vs. Fire Giant Dreadnought is the first that comes to mind which has been examined, where "Plate" would be sometimes AC 18 no dex, or sometimes AC 17 no dex or AC 18+Dex.
How hard is it to use in play? "This monster has an AC 15 with natural armor. It just received +2 Dexterity, but I don't have any basis for whether that's Natural Armor 15 no dex, or Natural Armor 13+Dex, or Natural Armor 13+Dex to a maximum of +2... let's argue about it for 20 minutes!
Option 3 (Saga in most posts, Texas): Monster armor is just an arbitrary number, with no calculation behind it.
Examples of monsters it doesn't work for: Fire Giant Dreadnought, since the DM is directed (or at least, it implies that they should) to recalculate AC when shields get dropped. But really, I suppose it doesn't CONTRADICT many stat blocks, its just an arguably very unhelpful way to think about them.
How hard is it to use in play? "This monster has an AC 15 with natural armor. It just received +2 Dexterity. That does nothing."
Of the three options, only Option 1 has any textual support. Option 2 requires a lot of houseruling and has no textual support, but a DM could probably make it work in a fair way if they're willing to work something out without worrying about RAW. But Option 3 not only devoid of textual support, it also directly contradicts the MM introduction. It is blasphemy.
Look, we have basically three options presented so far:
Option 1 (Chicken_Champ): Monster armor is always Dex+(some number or numbers representing armor in parenthesis).
Source: MM introduction, Armor Class: "A monster that wears armor or carries a shield has an Armor Class (AC) that takes its armor, shield, and Dexterity into account. Otherwise, a monster’s AC is based on its Dexterity modifier and natural armor, if any. If a monster has natural armor, wears armor, or carries a shield, this is noted in parentheses after its AC value."
Examples of monsters it doesn't work for? Zero.
How hard is it to use in play? "This monster has an AC 15 with natural armor. It just received +2 Dexterity, so now its AC is 16."
Option 2 (Doug_Booshaka, Lyxen, some of Saga's posts but not others): Monster armor is similar to player armor, so "heavy armor" ignores Dex, while "medium armor" might cap Dex bonus to a certain amount, and we should look to the PHB player armors for same/similar named armors to figure out if armor is light, medium, or heavy.
Source: No source.
Examples of monsters it doesn't work for? Countless. The fact that Plate results in a different calculation for Fire Giant vs. Fire Giant Dreadnought is the first that comes to mind which has been examined, where "Plate" would be sometimes AC 18 no dex, or sometimes AC 17 no dex or AC 18+Dex.
How hard is it to use in play? "This monster has an AC 15 with natural armor. It just received +2 Dexterity, but I don't have any basis for whether that's Natural Armor 15 no dex, or Natural Armor 13+Dex, or Natural Armor 13+Dex to a maximum of +2... let's argue about it for 20 minutes!
Option 3 (Saga in most posts, Texas): Monster armor is just an arbitrary number, with no calculation behind it.
Examples of monsters it doesn't work for: [Tooltip Not Found], since the DM is directed (or at least, it implies that they should) to recalculate AC when shields get dropped. But really, I suppose it doesn't CONTRADICT many stat blocks, its just an arguably very unhelpful way to think about them.
How hard is it to use in play? "This monster has an AC 15 with natural armor. It just received +2 Dexterity. That does nothing."
Of the three options, only Option 1 has any textual support. Option 2 requires a lot of houseruling and has no textual support, but a DM could probably make it work in a fair way if they're willing to work something out without worrying about RAW. But Option 3 not only devoid of textual support, it also directly contradicts the MM introduction. It is blasphemy.
Where you're going wrong is in thinking that there's a meaningful distinction between option 1 and option 3 in practice. Though you've thus far completely ignored it, there's solid evidence that, in the case of option 1, there's not any meaning whatsoever to the armor being worn. "Plate" can mean AC 18 or AC 17 or AC 15 depending on the monster, which means what's actually going on is option 3: the designers just picked a number.
[EDIT] I also want to be clear that my actual stated position is that it could be any one of these, and there's no textual support for any one of them over any other. Option 2 "takes armor, shield, and dexterity into account" just as much as option 1 does. You only think it doesn't because you're making unfounded assumptions about what "takes into account" means. Option 3 can do that: it just doesn't make any difference.
The designers picked a random number for that Plate, that's true. Erinyes Plate suuuuucks, apparently! But once again, the MM Introduction explicitly tells us that the armor has a mechanical effect on the creature's AC, and "not any meaning whatsoever to the armor being worn" is explicitly in contravention of RAW.
If your Forge Cleric blesses the Erinyes armor? It goes up +1 AC, it doesn't stay the same. If you slap a magic ring on them that gives them +2 Dex? It goes up +1 AC. It's a very simple, very uncomplicated system: monster armor has no complicated caps and formulas like player armor, because it doesn't say it does. Its just a number, that is the total of whatever their base AC is, plus dexterity, plus armor, plus shields, plus natural armor, etc. And that isn't a guess... it's what the MM says. There is no language anywhere suggesting or claiming otherwise.
[EDIT] I also want to be clear that my actual stated position is that it could be any one of these, and there's no textual support for any one of them over any other. Option 2 "takes armor, shield, and dexterity into account" just as much as option 1 does. You only think it doesn't because you're making unfounded assumptions about what "takes into account" means. Option 3 can do that: it just doesn't make any difference.
Option 2 would work, I was pretty clear that it's superior to option 3. It just also involves a lot of houseruling to figure out what kind of armor "patchwork armor" is, or why there's different kinds of plate. Option 1 doesn't require that, so is superior.
The designers picked a random number for that Plate, that's true. Erinyes Plate suuuuucks, apparently! But once again, the MM Introduction explicitly tells us that the armor has a mechanical effect on the creature's AC, and "not any meaning whatsoever to the armor being worn" is explicitly in contravention of RAW.
If your Forge Cleric blesses the Erinyes armor? It goes up +1 AC, it doesn't stay the same. If you slap a magic ring on them that gives them +2 Dex? It goes up +1 AC. It's a very simple, very uncomplicated system: monster armor has no complicated caps and formulas like player armor, because it doesn't say it does. Its just a number, that is the total of whatever their base AC is, plus dexterity, plus armor, plus shields, plus natural armor, etc. And that isn't a guess... it's what the MM says. There is no language anywhere suggesting or claiming otherwise.
The MM never says "AC is 10 + dex modifier + [arbitrary armor bonus]." It says the AC is based on those things, or takes those things into account. There is no language anywhere suggesting or claiming that the latter means the former. Again, normal PC armor rules for medium armor take both armor and dexterity into account. It's based on both of those things. But increasing someone's dex from 16 to 18 won't change their AC. Since we know for a fact that the game already uses calculations that do everything the Monster Manual says monster ACs do but don't do what you want them to do, there's no reason to think your idea is any better-founded than anything else.
If you refuse to even acknowledge the unfounded premises you're assuming, there's no point in discussing this with you, and I should have admitted that several posts ago.
I have agreed twice now, and this post makes three: what you're describing is Option 2 (don't just take Dex+somenumber (representing one or more armors) ), but instead try to figure out what the armor calculation of that armor might be, and how it incorporates Dexterity. That's fine, and would comply with the MM intro.... but would also require a lot of unwritten extra interpretation, to figure out why Plate works differently on some monsters than others, what kind of armor Patchwork Armor is, and whether all Natural Armor acts like Light Armor or might instead might sometimes be like Natural medium or Natural heavy (tortle?) armor. It's fine. It's just complicated, hard to arbitrate, and requires a lot of rulings beyond the MM.
I am acknowledging it. I am rejecting Option 2 as requiring more assumptions than Option 1, but it's certainly not as bad as Option 3.
What I am not seeing is any justification for your originally stated Option 3 (AC 15 is AC 15, and has nothing to do with armor or dexterity in any way that will allow ability score or equipment modifications to update the statblock). If you've got an argument for why Option 3 isn't a contradiction of the MM intro, I've yet to hear it. If you're jumping ship off of Option 3 and into Option 2, fine, guess that just leaves Texas.
What I'm also not seeing is where I've assumed an unfounded premise? You don't need to assume base 10 AC if you don't want to. Monster armor class is Dex+X, where X is either unarmored base AC, Natural Armor, Manufactured armor, or possibly even several seperate numbers adding together (as in the case of the Fire Giant Dreadnought, who gets AC from Plate, and Shield 1, and Shield 2).
SagaTympana's initial comment about monsters not having to follow player rules is technically correct. But in practice monsters almost always do follow the rules when they're wearing armor. Examples of monsters with heavy armor that are clearly using the PC rules abound: hobgoblin, champion, air elemental myrmidon, bael, battleforce angel, erinyes, helmed horror, githyanki knight and fire giant (note its AC isn't affected by its negative DEX mod.) Heck, even animated armor has AC appropriate for full plate despite technically not wearing plate. Cases like the fire giant dreadnought are pretty rare and usually a deliberate choice to make that monster unique.
All the "standard" giants (Hill, Stone, Cloud, Fire, Frost, Storm) that don't wear armor have natural armor to a varying degree (AC 13 for Hill, 14 for Cloud, 17 for Stone), and the three that wear armor, two are standards (Fire wears plate for a flat 18, Storm wears scale for 14+2 from its DEX). So all of them "work" with the standards set by the MM.
The two ways that Patchwork Armor would likewise work is if it is either 1) a medium armor better than half plate (at 16 + DEX mod, max 2), or 2) a heavy armor between Ring and Chain Mail (Flat AC 15). Given that the medium armor route would create an armor type better than the best listed medium armor, and the lack of an AC 15 heavy armor, my personal inclination would be to call it a heavy armor with flat AC 15.
But a DM wanting to work backwards and comply with the MM/PH rules could choose either method. Or do something different. Without a direct reference, its really DM fiat anyway.
The point is that they follow the rules until it's inconvenient, and then they throw the rules out the window. If you think the design of some monsters isn't entirely arbitrary, or that the designers have never started with a target AC and then just made @%$# up to reach that target, or that different designers have used different logic when creating content, you have not payed much attention to 5e monster design.
Monsters are in the DM's realm, and are beholden to very little. As evidenced by the Erinyes example here, armor can provide any value of AC and simply by calling it "heavy" you can choose to ignore dexterity. Or you can go the Will-o'-wisp route and give a monster insane, god-level dexterity that is not referenced anywhere in its description or abilities simply because you want to reflect that it is tiny and thus hard to hit. Don't try to insist that there's a unifying theory behind AC in monster design, because in practice (despite the MM guidelines) there's just not.
End of story, monsters cannot have an AC calculation that does not include a dexterity bonus.
Unfortunately this isn't true, as monsters can wear Heavy Armour, which doesn't add their dex bonus, such as Fire Giant's which wear plate armour and have 18ac.
Going back to the topic at hand: the Monster Manual states that Frost Giant's typically wear armour that consists of stringing together smaller creatures armour, such as a bunch of shields chained together.
Because a Frost Giant's Dexterity modifier is -1, this means a Frost Giant's patchwork armour is either Light or Medium armour with an ac of 16 + dex mod, or Heavy armour with an ac of 15. Annoyingly none of the armours in the armour section of the basic rules meet this criteria and Frost Giant's are the only creatures across the Monster Manual, Volo's and Mordenkainen's who wear 'Patchwork' armour (Just did a quick check) so we can't compare ac values with other creatures who wear them.
Personally I would assume it's Heavy Armour, otherwise we're assuming that you can string a bunch of shields together to make medium armour better than Half-Plate.
Monsters don't purport to have Light vs. Medium vs. Heavy armors, and their armors frequently behave differently from players. See e.g. the Fire Giant Dreadnought, whose dual shields are "each accounted for in the giant's AC". Confusingly, the DM is warned that the giant must "stow or drop one of its shields to hurl rocks," seeming to invite the DM to recalculate that AC when they do so... is each shield +2 AC? Is the first shield +2 AC, and the second +1 AC? Are they together +3 AC, but +0 AC if only one is held? If they're both +2 AC, is its Plate only AC 17 plate, instead of AC 18 plate like a regular Fire Giant? Ahhhhh....
But the math gets easier if there's a -1 AC from Dex in there. The Dreadnoughts AC is X base + Y plate +Z1 shield + Z2 shield + Dex = 21. That's all I know for sure. If X is 10 as usual, 10+Y+2Z-1=21, or Y+2Z=12, suggesting Y=8 and Z=2. 10+8+2+2-1=21. So every time the giant drops a shield, -2 AC.
Nice!
Why do you always twist yourselves into knots to come up with overly-complicated justifications?
A fire giant wears plate, thus giving it an AC of 18; regardless of it's Dexterity score of 9 (-1 modifier). With respect to the fire giant dreadnought, its AC of 21 is derived from a combination of "plate" and "shields". Since we know that "plate" is 18, "shields" must be worth +3. Setting aside one shield to throw a rock means we go from "shields" to "shield", and with that, its AC decreases to only 20. Does this break the normal rules that players work under? Yes. Does the preceding Monster Manual also state that monsters don't always follow the normal rules? Also yes.
The banshee'sCorrupting Touch is a melee spell attack that uses Dexterity for the attack roll; rather than a typical spellcasting ability. The wolf also uses Dexterity for its bite, but the dire wolf instead uses Strength when it attempts the same.
Monsters can, and often do, utilize armor that is available to players and their allied NPCs. There's even an entire sidebar dedicated to the warhorse wearing different barding. And, yes, this can mean their armor is heavy, medium, or light. Whether they have proficiency with any worn armor is up to the DM. And not every creature is proficient in its attacks. One doesn't have to look any further than the ghoul to see that.
The point is that they follow the rules until it's inconvenient, and then they throw the rules out the window.
This feels like a weird take to me. I look at it as the designers paying more attention to monsters having stats that work well in encounters instead of restricting themselves to making monsters follow the more restrictive player stat structures. In short, they focus on the what more than the how or the why.
The point is that they follow the rules until it's inconvenient, and then they throw the rules out the window.
This feels like a weird take to me. I look at it as the designers paying more attention to monsters having stats that work well in encounters instead of restricting themselves to making monsters follow the more restrictive player stat structures. In short, they focus on the what more than the how or the why.
Texas, that's clearly the instruction to DM's about how to craft their own monsters, as presented in the DMG: don't worry about the how or why, just settle on a "what" you want the monster's AC, HP, and attacks to look like, and reference their chart to find an appropriate CR to craft balanced encounters with. You're not wrong about that being an approach to monsters that the designers approve of...
...but only for DMs homebrewing new monsters for their own game. For the monsters published in the MM (and presumably, for all other published monsters in other sourcebooks as well?), the designers included language in the MM intro clearly communicating that the AC totals are the results of calculations that take armor and dexterity into account in some rational non-arbitrary way. Whether that's my "Option 1" approach (which I think is simplest), or the "Option 2" approach Coder, Jounichi, and now Saga prefer (which more closely tracks PHB expectations about armor, but occasionally requires making DM rulings about the parameters of novel armors like patchwork)... it's definitely one of those two approaches. "Option 3", arbitrary "it is what it is" AC that won't recalculate based on improved armor or improved Dexterity in any way just isn't an option for MM statblocks. And that's important, because players can and do turn into Beasts and other sorts of monsters, and then merge those forms with special spells, abilities, and magical equipment that alters those monster stats, so those AC numbers need to be rational calculations.
ARMOR CLASS A monster that wears armor or carries a shield has an Armor Class (AC) that takes its armor, shield, and Dexterity into account. Otherwise, a monster's AC is based on its Dexterity modifier and natural armor if any. If a monster has natural armor, wears armor, or carries a shield, this is noted in parentheses after its AC value.
The last sentence was bolded for emphasis.
So some monsters do, in fact, wear armor. If they do, this is described in parenthesis. But this does not necessarily have to be exhaustive. Goblins carry shields, but they cannot wear them while using their shortbow. We don't need the stat block to tell us this; we already have the Basic Rules (if nothing else) telling us so. And these rules are largely consistent. They need to be. There's a section on Armor and Weapon Swaps, found on page 342, that gives guidance on customizing creatures. Nevermind that player characters can also purchase barding for their bestial allies.
But we also know the above quote isn't exhaustive. It can't be; it's only three sentences long. For example, a mage may have their AC improved via casting mage armor on themself. It's not worn armor, but it still modifies their AC all the same. This tells us, without explicitly stating so, that there may be other descriptors which could go in the parenthesis.
And we know the value, even for items we assume to have a standard value, of what's in parenthesis could be anything. Natural armor doesn't have a uniform value. It varies anywhere from +1 (displacer beast) to +15 (tarrasque). This means we're free to adjust the value of whatever is in parenthesis; such as by giving a creature a magic item. In fact, Magic Items is its own little section on page 342, as well. Durnan, from Waterdeep: Dragon Heist, wears elven chain. And a werewolf, in their Hybrid or Wolf form, can even add their natural armor as a bonus to worn armor. This benefit even extends to PCs who contract the curse.
The exact statistics of the frost giant's "patchwork armor" are irrelevant. We don't need to know how much it weighs, or whether it imposes disadvantage on Dexterity (Stealth) checks. We just need to know what the AC will be if we change something. Usually, this is by changing what it already has equipped. But, if it helps, "They reuse the weapons and armor of their smaller foes, stringing shields into scale armor and lashing sword blades to wooden hafts to make giant-sized spears."
So maybe it's medium; if that matters to you. It's just stronger than the normal equivalent for its size.
The point is that they follow the rules until it's inconvenient, and then they throw the rules out the window.
This feels like a weird take to me. I look at it as the designers paying more attention to monsters having stats that work well in encounters instead of restricting themselves to making monsters follow the more restrictive player stat structures. In short, they focus on the what more than the how or the why.
Texas, that's clearly the instruction to DM's about how to craft their own monsters, as presented in the DMG: don't worry about the how or why, just settle on a "what" you want the monster's AC, HP, and attacks to look like, and reference their chart to find an appropriate CR to craft balanced encounters with. You're not wrong about that being an approach to monsters that the designers approve of...
...but only for DMs homebrewing new monsters for their own game. For the monsters published in the MM (and presumably, for all other published monsters in other sourcebooks as well?), the designers included language in the MM intro clearly communicating that the AC totals are the results of calculations that take armor and dexterity into account in some rational non-arbitrary way. Whether that's my "Option 1" approach (which I think is simplest), or the "Option 2" approach Coder, Jounichi, and now Saga prefer (which more closely tracks PHB expectations about armor, but occasionally requires making DM rulings about the parameters of novel armors like patchwork)... it's definitely one of those two approaches. "Option 3", arbitrary "it is what it is" AC that won't recalculate based on improved armor or improved Dexterity in any way just isn't an option for MM statblocks. And that's important, because players can and do turn into Beasts and other sorts of monsters, and then merge those forms with special spells, abilities, and magical equipment that alters those monster stats, so those AC numbers need to be rational calculations.
Please don't misrepresent my position. I've never said that "monster armor works just like PC armor," and we have numerous examples of PC armor rules producing results that do not align with monster stats. We also have numerous examples of PC armor rules producing results that do align with monster stats. Assuming your "option 2" may produce correct results in the most cases, but taking it as a rule clearly doesn't work.
Monsters are designed to provide a particular kind of challenge. If the designers can get a monster to have the AC they want it to by following standard equipment rules, then great! That's true in a lot of cases. But it's not always true, and the designers aren't afraid to modify the numbers with no clear explanation.
Noted. You've hopped back on the "the number is just a number" Option 3 bandwagon, but with the caveat that you think that that arbitrary number is usually chosen by the authors so as to closely align with a familiar armor calculation.
And yet... I see no link? I see no quote? Liar liar pants on fire. :)
dndbeyond.com forum tags
I'm going to make this way harder than it needs to be.
Says the person who has ignored the entire thread giving you examples of Monsters where Dex wasn't IN the AC calculation.
Hint - wanna know why there is no page reference for you there CC? The whole damn book is FULL of Monsters that break you opposed rule that you found that is wishy washy at best in being a true rule.
This violates the rule in the PHB that shields don't stack, and violates the Fire Giant entry in the Monster Manual, in which Fire Giants are AC 18 with Dex 9 while wearing plate. Said entry is proof by itself that Fire Giants in Plate with Dex modifier -1 are AC 18 base, not 17. On top of that, those Fireshields aren't dealing Improvised Weapon damage, which must mean they have a special rule governing that - most likely that they count as one-handed melee weapons. On the other hand, their only benefit from the second shield must be additional AC, or they wouldn't carry a second one. The most plausible set of ACs for the Giant, with 2/1/0 shields equipped, is 21/20/18 - you only need to assume the Giant's shields count as melee weapons and it has the top line from the Dual Wielder feat.
Note also the MTOF entries for Tortles and Tortle druids completely neglect to point out that Tortle AC won't go up with a higher Dexterity bonus. It's extremely normal for Monster entries to leave out vital details for calculating stuff like AC on the fly. We can reasonably conclude from all of the Giants entries - especially Storm Giant Quintessents - that all of these Giants are AC 10 + Dex + Natural Armor base, and then follow the usual armor rules (see Storm Giants, both flavors, and the Fire Giant base flavor for evidence).
As for OP: there's no way to know for certain whether the Patchwork Armor is functionally +1 Half Plate or +1 Ring Mail, because on a DexMod -1 wearer, they have the same AC. However, Frost Giant Everlasting Ones have the same AC, the same armor, the same DEX, everything - except they can Barbarian Rage only better, and Barbarian Rage doesn't work in Heavy Armor. I would therefore conclude Patchwork Armor is functionally +1 Half Plate, although I would not conclude it is necessarily magical. This also means their base AC is 9, of course. Note that D&D 5E armor never provides an AC bonus - it provides a distinct way to calculate your AC. You can rule any way you like on the armor, but my recommendation is as follows:
Maybe you missed it because it was on the last page, but I provided you a link.
Look, we have basically three options presented so far:
Option 1 (Chicken_Champ): Monster armor is always Dex+(some number or numbers representing armor in parenthesis).
Option 2 (Doug_Booshaka, Quindraco, Lyxen, some of Saga's posts but not others): Monster armor is similar to player armor, so "heavy armor" ignores Dex, while "medium armor" might cap Dex bonus to a certain amount, and we should look to the PHB player armors for same/similar named armors to figure out if armor is light, medium, or heavy.
Option 3 (Saga in most posts, Texas): Monster armor is just an arbitrary number, with no calculation behind it.
Of the three options, only Option 1 has any textual support. Option 2 requires a lot of houseruling and has no textual support, but a DM could probably make it work in a fair way if they're willing to work something out without worrying about RAW. But Option 3 not only devoid of textual support, it also directly contradicts the MM introduction. It is blasphemy.
dndbeyond.com forum tags
I'm going to make this way harder than it needs to be.
Where you're going wrong is in thinking that there's a meaningful distinction between option 1 and option 3 in practice. Though you've thus far completely ignored it, there's solid evidence that, in the case of option 1, there's not any meaning whatsoever to the armor being worn. "Plate" can mean AC 18 or AC 17 or AC 15 depending on the monster, which means what's actually going on is option 3: the designers just picked a number.
[EDIT] I also want to be clear that my actual stated position is that it could be any one of these, and there's no textual support for any one of them over any other. Option 2 "takes armor, shield, and dexterity into account" just as much as option 1 does. You only think it doesn't because you're making unfounded assumptions about what "takes into account" means. Option 3 can do that: it just doesn't make any difference.
The designers picked a random number for that Plate, that's true. Erinyes Plate suuuuucks, apparently! But once again, the MM Introduction explicitly tells us that the armor has a mechanical effect on the creature's AC, and "not any meaning whatsoever to the armor being worn" is explicitly in contravention of RAW.
If your Forge Cleric blesses the Erinyes armor? It goes up +1 AC, it doesn't stay the same. If you slap a magic ring on them that gives them +2 Dex? It goes up +1 AC. It's a very simple, very uncomplicated system: monster armor has no complicated caps and formulas like player armor, because it doesn't say it does. Its just a number, that is the total of whatever their base AC is, plus dexterity, plus armor, plus shields, plus natural armor, etc. And that isn't a guess... it's what the MM says. There is no language anywhere suggesting or claiming otherwise.
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Option 2 would work, I was pretty clear that it's superior to option 3. It just also involves a lot of houseruling to figure out what kind of armor "patchwork armor" is, or why there's different kinds of plate. Option 1 doesn't require that, so is superior.
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The MM never says "AC is 10 + dex modifier + [arbitrary armor bonus]." It says the AC is based on those things, or takes those things into account. There is no language anywhere suggesting or claiming that the latter means the former. Again, normal PC armor rules for medium armor take both armor and dexterity into account. It's based on both of those things. But increasing someone's dex from 16 to 18 won't change their AC. Since we know for a fact that the game already uses calculations that do everything the Monster Manual says monster ACs do but don't do what you want them to do, there's no reason to think your idea is any better-founded than anything else.
If you refuse to even acknowledge the unfounded premises you're assuming, there's no point in discussing this with you, and I should have admitted that several posts ago.
I have agreed twice now, and this post makes three: what you're describing is Option 2 (don't just take Dex+somenumber (representing one or more armors) ), but instead try to figure out what the armor calculation of that armor might be, and how it incorporates Dexterity. That's fine, and would comply with the MM intro.... but would also require a lot of unwritten extra interpretation, to figure out why Plate works differently on some monsters than others, what kind of armor Patchwork Armor is, and whether all Natural Armor acts like Light Armor or might instead might sometimes be like Natural medium or Natural heavy (tortle?) armor. It's fine. It's just complicated, hard to arbitrate, and requires a lot of rulings beyond the MM.
I am acknowledging it. I am rejecting Option 2 as requiring more assumptions than Option 1, but it's certainly not as bad as Option 3.
What I am not seeing is any justification for your originally stated Option 3 (AC 15 is AC 15, and has nothing to do with armor or dexterity in any way that will allow ability score or equipment modifications to update the statblock). If you've got an argument for why Option 3 isn't a contradiction of the MM intro, I've yet to hear it. If you're jumping ship off of Option 3 and into Option 2, fine, guess that just leaves Texas.
What I'm also not seeing is where I've assumed an unfounded premise? You don't need to assume base 10 AC if you don't want to. Monster armor class is Dex+X, where X is either unarmored base AC, Natural Armor, Manufactured armor, or possibly even several seperate numbers adding together (as in the case of the Fire Giant Dreadnought, who gets AC from Plate, and Shield 1, and Shield 2).
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SagaTympana's initial comment about monsters not having to follow player rules is technically correct. But in practice monsters almost always do follow the rules when they're wearing armor. Examples of monsters with heavy armor that are clearly using the PC rules abound: hobgoblin, champion, air elemental myrmidon, bael, battleforce angel, erinyes, helmed horror, githyanki knight and fire giant (note its AC isn't affected by its negative DEX mod.) Heck, even animated armor has AC appropriate for full plate despite technically not wearing plate. Cases like the fire giant dreadnought are pretty rare and usually a deliberate choice to make that monster unique.
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^ This is an example of an "Option 2" comment for the record.
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All the "standard" giants (Hill, Stone, Cloud, Fire, Frost, Storm) that don't wear armor have natural armor to a varying degree (AC 13 for Hill, 14 for Cloud, 17 for Stone), and the three that wear armor, two are standards (Fire wears plate for a flat 18, Storm wears scale for 14+2 from its DEX). So all of them "work" with the standards set by the MM.
The two ways that Patchwork Armor would likewise work is if it is either 1) a medium armor better than half plate (at 16 + DEX mod, max 2), or 2) a heavy armor between Ring and Chain Mail (Flat AC 15). Given that the medium armor route would create an armor type better than the best listed medium armor, and the lack of an AC 15 heavy armor, my personal inclination would be to call it a heavy armor with flat AC 15.
But a DM wanting to work backwards and comply with the MM/PH rules could choose either method. Or do something different. Without a direct reference, its really DM fiat anyway.
The point is that they follow the rules until it's inconvenient, and then they throw the rules out the window. If you think the design of some monsters isn't entirely arbitrary, or that the designers have never started with a target AC and then just made @%$# up to reach that target, or that different designers have used different logic when creating content, you have not payed much attention to 5e monster design.
Monsters are in the DM's realm, and are beholden to very little. As evidenced by the Erinyes example here, armor can provide any value of AC and simply by calling it "heavy" you can choose to ignore dexterity. Or you can go the Will-o'-wisp route and give a monster insane, god-level dexterity that is not referenced anywhere in its description or abilities simply because you want to reflect that it is tiny and thus hard to hit. Don't try to insist that there's a unifying theory behind AC in monster design, because in practice (despite the MM guidelines) there's just not.
My homebrew subclasses (full list here)
(Artificer) Swordmage | Glasswright | (Barbarian) Path of the Savage Embrace
(Bard) College of Dance | (Fighter) Warlord | Cannoneer
(Monk) Way of the Elements | (Ranger) Blade Dancer
(Rogue) DaggerMaster | Inquisitor | (Sorcerer) Riftwalker | Spellfist
(Warlock) The Swarm
Why do you always twist yourselves into knots to come up with overly-complicated justifications?
A fire giant wears plate, thus giving it an AC of 18; regardless of it's Dexterity score of 9 (-1 modifier). With respect to the fire giant dreadnought, its AC of 21 is derived from a combination of "plate" and "shields". Since we know that "plate" is 18, "shields" must be worth +3. Setting aside one shield to throw a rock means we go from "shields" to "shield", and with that, its AC decreases to only 20. Does this break the normal rules that players work under? Yes. Does the preceding Monster Manual also state that monsters don't always follow the normal rules? Also yes.
The banshee's Corrupting Touch is a melee spell attack that uses Dexterity for the attack roll; rather than a typical spellcasting ability. The wolf also uses Dexterity for its bite, but the dire wolf instead uses Strength when it attempts the same.
Monsters can, and often do, utilize armor that is available to players and their allied NPCs. There's even an entire sidebar dedicated to the warhorse wearing different barding. And, yes, this can mean their armor is heavy, medium, or light. Whether they have proficiency with any worn armor is up to the DM. And not every creature is proficient in its attacks. One doesn't have to look any further than the ghoul to see that.
This feels like a weird take to me. I look at it as the designers paying more attention to monsters having stats that work well in encounters instead of restricting themselves to making monsters follow the more restrictive player stat structures. In short, they focus on the what more than the how or the why.
"Not all those who wander are lost"
Texas, that's clearly the instruction to DM's about how to craft their own monsters, as presented in the DMG: don't worry about the how or why, just settle on a "what" you want the monster's AC, HP, and attacks to look like, and reference their chart to find an appropriate CR to craft balanced encounters with. You're not wrong about that being an approach to monsters that the designers approve of...
...but only for DMs homebrewing new monsters for their own game. For the monsters published in the MM (and presumably, for all other published monsters in other sourcebooks as well?), the designers included language in the MM intro clearly communicating that the AC totals are the results of calculations that take armor and dexterity into account in some rational non-arbitrary way. Whether that's my "Option 1" approach (which I think is simplest), or the "Option 2" approach Coder, Jounichi, and now Saga prefer (which more closely tracks PHB expectations about armor, but occasionally requires making DM rulings about the parameters of novel armors like patchwork)... it's definitely one of those two approaches. "Option 3", arbitrary "it is what it is" AC that won't recalculate based on improved armor or improved Dexterity in any way just isn't an option for MM statblocks. And that's important, because players can and do turn into Beasts and other sorts of monsters, and then merge those forms with special spells, abilities, and magical equipment that alters those monster stats, so those AC numbers need to be rational calculations.
The camps so far seem to be:
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Let's try this from scratch, shall we
The last sentence was bolded for emphasis.
So some monsters do, in fact, wear armor. If they do, this is described in parenthesis. But this does not necessarily have to be exhaustive. Goblins carry shields, but they cannot wear them while using their shortbow. We don't need the stat block to tell us this; we already have the Basic Rules (if nothing else) telling us so. And these rules are largely consistent. They need to be. There's a section on Armor and Weapon Swaps, found on page 342, that gives guidance on customizing creatures. Nevermind that player characters can also purchase barding for their bestial allies.
But we also know the above quote isn't exhaustive. It can't be; it's only three sentences long. For example, a mage may have their AC improved via casting mage armor on themself. It's not worn armor, but it still modifies their AC all the same. This tells us, without explicitly stating so, that there may be other descriptors which could go in the parenthesis.
And we know the value, even for items we assume to have a standard value, of what's in parenthesis could be anything. Natural armor doesn't have a uniform value. It varies anywhere from +1 (displacer beast) to +15 (tarrasque). This means we're free to adjust the value of whatever is in parenthesis; such as by giving a creature a magic item. In fact, Magic Items is its own little section on page 342, as well. Durnan, from Waterdeep: Dragon Heist, wears elven chain. And a werewolf, in their Hybrid or Wolf form, can even add their natural armor as a bonus to worn armor. This benefit even extends to PCs who contract the curse.
The exact statistics of the frost giant's "patchwork armor" are irrelevant. We don't need to know how much it weighs, or whether it imposes disadvantage on Dexterity (Stealth) checks. We just need to know what the AC will be if we change something. Usually, this is by changing what it already has equipped. But, if it helps, "They reuse the weapons and armor of their smaller foes, stringing shields into scale armor and lashing sword blades to wooden hafts to make giant-sized spears."
So maybe it's medium; if that matters to you. It's just stronger than the normal equivalent for its size.
Please don't misrepresent my position. I've never said that "monster armor works just like PC armor," and we have numerous examples of PC armor rules producing results that do not align with monster stats. We also have numerous examples of PC armor rules producing results that do align with monster stats. Assuming your "option 2" may produce correct results in the most cases, but taking it as a rule clearly doesn't work.
Monsters are designed to provide a particular kind of challenge. If the designers can get a monster to have the AC they want it to by following standard equipment rules, then great! That's true in a lot of cases. But it's not always true, and the designers aren't afraid to modify the numbers with no clear explanation.
Noted. You've hopped back on the "the number is just a number" Option 3 bandwagon, but with the caveat that you think that that arbitrary number is usually chosen by the authors so as to closely align with a familiar armor calculation.
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