You are technically correct. The normal don/doff rules don't give any indication that the 5 minutes it takes to don scale requires anything that a fish couldn't do; to be fair, a fish could spend 5 minutes donning fish scale if that only requires sitting around with the armor for a while. On the other hand, if you think you actually have to spend that time doing some sort of interacting with the armor, then the armorer ability only changes how long that takes.
But either way, it now negates the bonus action of casting wild shape.
it is also an action to doff. Or are you saying you can don donned armor?
That's covered under Wildshape:
You choose whether your equipment falls to the ground in your space, merges into your new form, or is worn by it. Worn equipment functions as normal, but the DM decides whether it is practical for the new form to wear a piece of equipment, based on the creature's shape and size. Your equipment doesn't change size or shape to match the new form, and any equipment that the new form can't wear must either fall to the ground or merge with it. Equipment that merges with the form has no effect until you leave the form.
The player has the option for the armor to fall to the ground. So free doffing as a part of wildshape.
Granted, if a DM argues that it's not practical for the new form to be wearing the armor I'd find it unlikely that the same DM would also allow the donning action to reshape the armor in the moment.
There's a lot of misunderstanding and irrelevant tangents in this thread, specifically with these three arguments:
The whole argument over the description of "form-fitting" is a complete red herring. The form-fitting description of the arcane armor is not relevant to either side of the argument because it only describes the armor tightening up around your body, not changing its entire shape to fit your body.
The argument about whether or not an animal form has the dexterity to manipulate and equip the armor is also completely irrelevant. From the description of the armor taking only an action to don, there's no way that you are actually lightning fast manually equipping a full set of armor, including boots, greaves, breastplate, gauntlets, helm, etc in 6 seconds. You can't even put on average everyday work clothes in 6 seconds, let alone a full suit of armor. Based on the duration to don the armor, the fact that it's a magical armor specifically attuned to your character's body, and this lore post describing the armor: "She strode across the room and placed her hand on the chest piece of her Mark 1 Guardian. Its plates shuddered at her touch, then sprung to life and rolled down her arm like an army of dully glinting beetles. In seconds, there was a click as the metal plates which had slithered over her body snapped into place.", we can very safely say that the arcane armor magically dons itself to your body, no opposable thumbs required.
The material of the armor is not relevant. Arcane armor very clearly allows for the armor to be non-metallic, as nowhere does it say the armor must be made of metal, and nowhere does it provide a list of only approved armor types that can be used. This means leather armor is absolutely an option. In addition, this argument is yet another red herring, because it doesn't actually matter if the armor is made of metal. The whole "druids never use metal" thing is purely a lore suggestion and not an actual game mechanic. As we've seen recently with all of the options for players to customize their racial features and lineages, D&D very clearly treats lore-specific rules with a massive grain of salt. This means the whole "druids never use metal" trope is very outdated and over-exaggerated. Most druids may shun metal, but that doesn't mean it's an immovable requirement of the class.
There are really only two rules that come into play with druids and arcane armor:
WIld Shape
You choose whether your equipment falls to the ground in your space, merges into your new form, or is worn by it. Worn equipment functions as normal, but the DM decides whether it is practical for the new form to wear a piece of equipment, based on the creature’s shape and size. Your equipment doesn’t change size or shape to match the new form, and any equipment that the new form can’t wear must either fall to the ground or merge with it. Equipment that merges with the form has no effect until you leave the form.
Arcane Armor
You gain the following benefits while wearing this armor:
If the armor normally has a Strength requirement, the arcane armor lacks this requirement for you.
You can use the arcane armor as a spellcasting focus for your artificer spells.
The armor attaches to you and can’t be removed against your will. It also expands to cover your entire body, although you can retract or deploy the helmet as a bonus action. The armor replaces any missing limbs, functioning identically to a limb it replaces.
You can doff or don the armor as an action.
These are two apparently conflicting rules, because wildshape provides a blanket general rule that no armor changes shape to match your new form, while arcane armor provides a rule that this specific armor expands to cover your entire body.
As we know, one of the most fundamental rules of D&D is that specific rules override general rules. This means that because wild shape provides a blanket rule for all armor, while arcane armor applies only to this one specific set of armor, the rules for arcane armor can override the rules for wild shape.
As has been mentioned previously, wild shape allows you to drop your armor to the ground. This means it is possible to use a bonus action to wild shape and drop your arcane armor, then use your action to don the armor. However, depending on your interpretation of the rules, this may not even be needed. The rules for arcane armor do not say the armor expands to cover your entire body when you don the armor; they say the armor expands to cover your entire body while wearing the armor. This opens the probable interpretation for the armor to dynamically adapt itself to your current form. However, this is a tangent, because regardless of whether or not you need to doff the armor and re-don it in order for it to cover your body, it still depends on one prime question...
There is really only one prime question to be answered when it comes to determining whether or not a druid can use arcane armor in their animal form: Does "expanding to cover your entire body" only mean the body you designated when you created the armor, or does it mean your current body? This question is up to your DM to interpret, but none of the other arguments presented in this thread really matter aside from this question.
I think the portion of text in wild shape highlighted saying that gear doesn’t reshape is more of a limitation about the wild shape feature.
The wild shape feature itself doesn’t give the ability to reshape equipment.
I don’t understand how when we read the text we give the class specific feature the ability to negate how magic items potentially work.
that being said, I don’t have a dog in this fight. I don’t think I’ll ever play a druid, and if I do it won’t be a circle of the moon. No one I play with has expressed interest in that class at all either.
I would just like to add another thought that had just occurred to me now.
"The armor replaces any missing limbs, functioning identically to a limb it replaces"
So not only could it potentially adapt itself to your new wildshape, it could adapt itself as a humanoid form that can be comfortably worn by your new wildshape, replacing your normal limbs.
If a fish has all its limbs, it isn't missing any.
Well said, I think you summarized everything previously said of note, and brought up something I hadn’t though of before, “The rules for arcane armor do not say the armor expands to cover your entire body when you don the armor; they say the armor expands to cover your entire body while wearing the armor.”
However I think your prime question might be a bit off... nowhere, that I’ve found, does say wild shape gives you a new body, just changes to its form, always using the words “transform” or “emulate,” or “magically assume the shape of...”
“Whether calling on the elemental forces of nature or emulating the creatures of the animal world, druids are an embodiment of nature’s resilience, cunning, and fury. They claim no mastery over nature. Instead, they see themselves as extensions of nature’s indomitable will.”
Perhaps there is some lore centric writing describing how the form changes, but every time I’ve heard it explained is the druids body molds and expands/contracts to fit the new form, sort of like the animorphs. So imho, same body, different form.
CadensCavalry, I would agree with you! Personally if one of my players brought this question to me I would absolutely allow arcane armor to be used by wild shapes.
In my interpretation there is really nothing in the rules that prohibits arcane armor from adapting to your changing body, but since this seems to be a contentious topic I figured I'd try to play devil's advocate to find any arguments against this functionality, and that was the only one I could find, weak though it is.
My general thoughts on this subject are that I do not believe it is allowed by RAW, but if a player of mine has decided to pair two very divergent classes for this specific purpose... I'd probably allow it. The only thing this combo really brings to the table is a higher AC for their otherwise completely normal Wild Shape stats. Hitting them with stuff that requires saving throws, and the good-old-fashioned Heat Metal is gonna shut that shit down hard like always.
As for the "not RAW" aspect, there are two elements regarding the characteristics of a physical object that are pertinent: shape, and size. A suit of armor is shaped to fit a certain type of creature's biology--a piece of leg armor for a standard bipedal humanoid is shaped to work with that skeletal structure & forward-jointed knee. Altering the size (specific dimensions) of Arcane Armor doesn't change the general shape that the armor takes. Arcane Armor shaped for a typical humanoid doesn't change shape to fit a bear.
You don't know what fear is until you've witnessed a drunk bird divebombing you while carrying a screaming Kobold throwing fire anywhere and everywhere.
I would just like to add another thought that had just occurred to me now.
"The armor replaces any missing limbs, functioning identically to a limb it replaces"
So not only could it potentially adapt itself to your new wildshape, it could adapt itself as a humanoid form that can be comfortably worn by your new wildshape, replacing your normal limbs.
If a fish has all its limbs, it isn't missing any.
If a human is turned into a fish, do they still have their limbs?
As for the "not RAW" aspect, there are two elements regarding the characteristics of a physical object that are pertinent: shape, and size. A suit of armor is shaped to fit a certain type of creature's biology--a piece of leg armor for a standard bipedal humanoid is shaped to work with that skeletal structure & forward-jointed knee. Altering the size (specific dimensions) of Arcane Armor doesn't change the general shape that the armor takes. Arcane Armor shaped for a typical humanoid doesn't change shape to fit a bear.
Where are you getting this interpretation that arcane armor doesn't change it's shape to fit your body? Remember, arcane armor is not a regular piece of armor. If it was then your interpretation would be completely valid, but there is only one description of the armor's ability to change shape, and it states:
You gain the following benefits while wearing this armor:
The armor attaches to you and can’t be removed against your will. It also expands to cover your entire body...
Nowhere in this description of the armor does it say the armor only expands to cover a specific, predefined part of your body. It says it expands to cover your entire body. A RAW interpretation of that is that it...well... expands to cover your entire body. This means if your body is a humanoid, it expands to cover your entire humanoid body. If your body is a bear, it expands to cover your entire bear body.
I could see a RAI interpretation limiting the ability of the arcane armor to cover your body if you wild shape into something really small (like an insect) or really massive (like an elephant), but RAW there is really nothing stopping druid from using arcane armor in wild shape.
I would just like to add another thought that had just occurred to me now.
"The armor replaces any missing limbs, functioning identically to a limb it replaces"
So not only could it potentially adapt itself to your new wildshape, it could adapt itself as a humanoid form that can be comfortably worn by your new wildshape, replacing your normal limbs.
If a fish has all its limbs, it isn't missing any.
If a human is turned into a fish, do they still have their limbs?
They're not missing any.
So they still have their arms and legs then? If they want to walk on land they can?
I think the key point you're missing is that when you wild shape into an animal, you are no longer a humanoid. You are now the animal you wild shaped into. This means if you wild shape into a fish then you are not missingyour arms and legs, because a fish does not have arms and legs. A fish is not supposed to have arms and legs, so when you are a fish you have all of your proper limbs.
You can't be missing something that you're not supposed to have, and because you're no longer a humanoid, you're no longer supposed to have humanoid limbs.
So, presuming that this works (considering the contention some have demonstrated, that is a big presumption), spending a bonus action to wild shape then an action to don the arcane armor, maybe we could take a moment to discuss the greater implications, both beneficial and potential pitfalls. Before that, one key point - armor doesn’t come as a suit. Breastplate doesn’t come with boots, nor gauntlets, nor a helm, not even pants (don’t know what you call armored pants). Therefore any of the aforementioned armor pieces are generated when the armor “expands to cover” the entire body. (Noted exclusions to the above statement include heavy armor and scale mail)
guardian armor - thunder damage gauntlets. If you shape change into a dire wolf, which while it doesn’t have hands, the armor will still expand over the paws. A reasonable dm may let you use the ‘gauntlet’ attack using paws. Also there is a bonus action that provides temp HP a certain number of times, no anatomical structure differences seem to restrict this.
infiltrator armor - sticking with the dire wolf example (though I encourage others to bring forward their own examples for discussion) the lightning launchers can be ‘gauntlet’ mounted or mounted on the chest (RAW). Reasonably it might be difficult for a wolf to aim a paw, which might cause someone to say the word dexterity, however all of the armorers arcane weapons use INT. To forego this argument simply mount the launcher to your chest (a listed option). I see no reason the advantage to stealth rolls wouldn’t also be in effect.
The following is the one major issue I see with this build; what happens to the armor when the wild shape is dropped, willingly or unwillingly? RAW, the best possible option I could see is that you could choose for the armor to fall to the ground. Either that, or it remains in the form it was in when you were wild shaped, potentially protecting you, but trapping you in place until you use an action to re-don the armor, or a bonus action to wild shape again. I say this since, as previously discussed, wild shape doesn’t cause the armor to change size and the arcane armor only expands to cover your entire body, it does not contract. If you have a forgiving dm they may allow you to revert to your normal form and continue wearing the armor “if your dm deems it reasonable.” the above would be the best available raw potentials, though I certainly think the flavor of armorer, masters of their magic and craft, could do better. That kind of non-RAW is tap to DM specifications
As for the "not RAW" aspect, there are two elements regarding the characteristics of a physical object that are pertinent: shape, and size. A suit of armor is shaped to fit a certain type of creature's biology--a piece of leg armor for a standard bipedal humanoid is shaped to work with that skeletal structure & forward-jointed knee. Altering the size (specific dimensions) of Arcane Armor doesn't change the general shape that the armor takes. Arcane Armor shaped for a typical humanoid doesn't change shape to fit a bear.
Where are you getting this interpretation that arcane armor doesn't change it's shape to fit your body? Remember, arcane armor is not a regular piece of armor. If it was then your interpretation would be completely valid, but there is only one description of the armor's ability to change shape, and it states:
You gain the following benefits while wearing this armor:
The armor attaches to you and can’t be removed against your will. It also expands to cover your entire body...
Nowhere in this description of the armor does it say the armor only expands to cover a specific, predefined part of your body. It says it expands to cover your entire body. A RAW interpretation of that is that it...well... expands to cover your entire body. This means if your body is a humanoid, it expands to cover your entire humanoid body. If your body is a bear, it expands to cover your entire bear body.
I could see a RAI interpretation limiting the ability of the arcane armor to cover your body if you wild shape into something really small (like an insect) or really massive (like an elephant), but RAW there is really nothing stopping druid from using arcane armor in wild shape.
Nowhere in the description of the armor does it say that the armor changes shape.
Arcane Armor
Beginning at 3rd level, your metallurgical pursuits have led to you making armor a conduit for your magic. As an action, you can turn a suit of armor you are wearing into Arcane Armor, provided you have smith's tools in hand.
You gain the following benefits while wearing this armor:
If the armor normally has a Strength requirement, the arcane armor lacks this requirement for you.
You can use the arcane armor as a spellcasting focus for your artificer spells.
The armor attaches to you and can’t be removed against your will. It also expands to cover your entire body, although you can retract or deploy the helmet as a bonus action. The armor replaces any missing limbs, functioning identically to a body part it is replacing.
The armor continues to be Arcane Armor until you don another suit of armor or you die.
You have to be wearing the armor to begin with, so it has to start with the condition of armor that is shaped for your character's normal body type. Expansion is a function of size, not shape. Tailoring a shirt for perfect fit isn't a function of shape; the generic shape of a shirt for the human body remains the same, but the dimensions of the sleeve/cuff/neck/chest/shoulders are adjusted to perfectly fit your human body. The tailor isn't able to take a human shirt and adjust it to fit a bear.
The more I think about it, the more I think that I wouldn't allow my players to do this at all. I didn't think about the benefits of Armor Model, Armor Modifications, and Perfected Armor. None of this is meant to work with Wild Shape.
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You don't know what fear is until you've witnessed a drunk bird divebombing you while carrying a screaming Kobold throwing fire anywhere and everywhere.
You have to be wearing the armor to begin with, so it has to start with the condition of armor that is shaped for your character's normal body type. Expansion is a function of size, not shape. Tailoring a shirt for perfect fit isn't a function of shape; the generic shape of a shirt for the human body remains the same, but the dimensions of the sleeve/cuff/neck/chest/shoulders are adjusted to perfectly fit your human body. The tailor isn't able to take a human shirt and adjust it to fit a bear.
The more I think about it, the more I think that I wouldn't allow my players to do this at all. I didn't think about the benefits of Armor Model, Armor Modifications, and Perfected Armor. None of this is meant to work with Wild Shape.
If we're going to get super pedantic with the words, keep in mind the description of the armor does not say that it expands to fit your body. It says the armor expands to cover your body. You do not need boots or a helmet to create the arcane armor (a suit of armor need not cover the entire body in order to be considered a suit), but the arcane armor does create these for you. This means if you use a suit of armor that does not include a helmet, or even if you use a suit of armor that has an open-faced helmet, the fact that the end result of the arcane armor covers your entire body means the armor must change its original shape. Even if the usage of the word 'expand' suggests it only changes size, the usage of the word 'cover' does suggest it changes its shape.
Also, the state of the armor when you create it does not matter, because the function of expanding to cover your body occurs any time you are wearing the armor, not just when you create the armor.
Whether or not the armor was meant to work with wild shape is also not really relevant. D&D (or literally any other game) is all about finding the creative solutions that perhaps no one else has thought of, as long as those solutions are not exploits (ie breaking the rules). The benefits of a player in wild shape using arcane armor really don't make that player more powerful than they could be with other multiclass options, nor do the benefits significantly outweigh the penalties a druid incurs by taking a minimum of 3 levels of artificer (or vice-versa, an artificer taking 2 levels of druid). There's no lore reason or game balance reason for arcane armor to not be used during wild shape, so the only argument left against it is whether or not it breaks the rules.
Like I said originally, this is indeed the prime question of whether or not arcane armor can be used with wild shape: Does the arcane armor expand to cover only the body you had when you first created the armor? Or does the armor expand to cover your current body? Nowhere in the rules is the first interpretation spelled out, and as I said before, there is a difference between armor changing to fit your body versus the armor changing to cover your body, so my interpretation would be that the armor expands to cover your current body, regardless of what your current body is.
Regardless, like so many other things in D&D, the fact that both of our arguments essentially come down to one or two word choices means that this a gray area, and so unless we receive a Sage Advice post on it, there will not be any single true answer. Your interpretation is just as valid as mine and if someone wants to create a druid/artificer multiclass with this feature in mind, they better make sure they talk to their own DM about it first, because regardless of our debate, that will be the only thing that matters.
You are right, it is a grey area. In fact, the wild shape rules even say it is up to the DM. All we know is that the default state of the game is that any particular piece of armor fits any particular humanoid character within reason, seemingly adjusting size to fit; It is explicitly stated that magic items automatically resize to fit; the armorer gains a similar ability allowing armor to expand to cover a character; and the Druid’s ability explicitly says that armor doesn’t change size to fit beast forms. Oh Yeah, and it is up to the DM to determine if a particular bit of equipment is reasonable for a beast to wear.
Edit: Oh, and there is a variant rule about equipment sizes.
Does this build straddle the fence as far as rules are concerned? Yes.
Would it be absolutely broken, especially if combined with a Kalashtar Bear Totem Barbarian? Yes.
Is it epic? Yes.
Would I allow it? No.
It would be particularly bad mixed with 3 levels of Barbarian, assuming you're answering the OP, who wanted to do this with ring mail a year and a half ago. Rage benefits don't apply in heavy armor. There's also nothing to straddle except for discussing whether or not Druids can wear ring mail, which we don't have any RAW clarification on - provided you remove that headache and discuss only armor the Druid will willingly wear, the only potential issue is whether or not the armor will change shape with the Druid, and that discussion can be avoided as well by choosing barding as the target armor to turn into Arcane Armor - e.g. for a Druid who habitually turns into a dire wolf, all you need is studded leather barding for a Dire Wolf and the only RAW concerns in this thread are rendered moot.
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You are technically correct. The normal don/doff rules don't give any indication that the 5 minutes it takes to don scale requires anything that a fish couldn't do; to be fair, a fish could spend 5 minutes donning fish scale if that only requires sitting around with the armor for a while. On the other hand, if you think you actually have to spend that time doing some sort of interacting with the armor, then the armorer ability only changes how long that takes.
But either way, it now negates the bonus action of casting wild shape.
it is also an action to doff. Or are you saying you can don donned armor?
That's covered under Wildshape:
The player has the option for the armor to fall to the ground. So free doffing as a part of wildshape.
Granted, if a DM argues that it's not practical for the new form to be wearing the armor I'd find it unlikely that the same DM would also allow the donning action to reshape the armor in the moment.
I guess that depends on how your dm interpret “expands to cover your entire body.”
There's a lot of misunderstanding and irrelevant tangents in this thread, specifically with these three arguments:
Based on the duration to don the armor, the fact that it's a magical armor specifically attuned to your character's body, and this lore post describing the armor: "She strode across the room and placed her hand on the chest piece of her Mark 1 Guardian. Its plates shuddered at her touch, then sprung to life and rolled down her arm like an army of dully glinting beetles. In seconds, there was a click as the metal plates which had slithered over her body snapped into place.", we can very safely say that the arcane armor magically dons itself to your body, no opposable thumbs required.
In addition, this argument is yet another red herring, because it doesn't actually matter if the armor is made of metal. The whole "druids never use metal" thing is purely a lore suggestion and not an actual game mechanic. As we've seen recently with all of the options for players to customize their racial features and lineages, D&D very clearly treats lore-specific rules with a massive grain of salt. This means the whole "druids never use metal" trope is very outdated and over-exaggerated. Most druids may shun metal, but that doesn't mean it's an immovable requirement of the class.
There are really only two rules that come into play with druids and arcane armor:
WIld Shape
Arcane Armor
These are two apparently conflicting rules, because wildshape provides a blanket general rule that no armor changes shape to match your new form, while arcane armor provides a rule that this specific armor expands to cover your entire body.
As we know, one of the most fundamental rules of D&D is that specific rules override general rules. This means that because wild shape provides a blanket rule for all armor, while arcane armor applies only to this one specific set of armor, the rules for arcane armor can override the rules for wild shape.
As has been mentioned previously, wild shape allows you to drop your armor to the ground. This means it is possible to use a bonus action to wild shape and drop your arcane armor, then use your action to don the armor. However, depending on your interpretation of the rules, this may not even be needed. The rules for arcane armor do not say the armor expands to cover your entire body when you don the armor; they say the armor expands to cover your entire body while wearing the armor. This opens the probable interpretation for the armor to dynamically adapt itself to your current form. However, this is a tangent, because regardless of whether or not you need to doff the armor and re-don it in order for it to cover your body, it still depends on one prime question...
There is really only one prime question to be answered when it comes to determining whether or not a druid can use arcane armor in their animal form: Does "expanding to cover your entire body" only mean the body you designated when you created the armor, or does it mean your current body? This question is up to your DM to interpret, but none of the other arguments presented in this thread really matter aside from this question.
I’m actually willing to admit i was probably wrong on this. It was just a thought that occurred to me.
I think the portion of text in wild shape highlighted saying that gear doesn’t reshape is more of a limitation about the wild shape feature.
The wild shape feature itself doesn’t give the ability to reshape equipment.
I don’t understand how when we read the text we give the class specific feature the ability to negate how magic items potentially work.
that being said, I don’t have a dog in this fight. I don’t think I’ll ever play a druid, and if I do it won’t be a circle of the moon. No one I play with has expressed interest in that class at all either.
If a fish has all its limbs, it isn't missing any.
Well said, I think you summarized everything previously said of note, and brought up something I hadn’t though of before, “The rules for arcane armor do not say the armor expands to cover your entire body when you don the armor; they say the armor expands to cover your entire body while wearing the armor.”
However I think your prime question might be a bit off... nowhere, that I’ve found, does say wild shape gives you a new body, just changes to its form, always using the words “transform” or “emulate,” or “magically assume the shape of...”
“Whether calling on the elemental forces of nature or emulating the creatures of the animal world, druids are an embodiment of nature’s resilience, cunning, and fury. They claim no mastery over nature. Instead, they see themselves as extensions of nature’s indomitable will.”
Perhaps there is some lore centric writing describing how the form changes, but every time I’ve heard it explained is the druids body molds and expands/contracts to fit the new form, sort of like the animorphs. So imho, same body, different form.
CadensCavalry, I would agree with you! Personally if one of my players brought this question to me I would absolutely allow arcane armor to be used by wild shapes.
In my interpretation there is really nothing in the rules that prohibits arcane armor from adapting to your changing body, but since this seems to be a contentious topic I figured I'd try to play devil's advocate to find any arguments against this functionality, and that was the only one I could find, weak though it is.
My general thoughts on this subject are that I do not believe it is allowed by RAW, but if a player of mine has decided to pair two very divergent classes for this specific purpose... I'd probably allow it. The only thing this combo really brings to the table is a higher AC for their otherwise completely normal Wild Shape stats. Hitting them with stuff that requires saving throws, and the good-old-fashioned Heat Metal is gonna shut that shit down hard like always.
As for the "not RAW" aspect, there are two elements regarding the characteristics of a physical object that are pertinent: shape, and size. A suit of armor is shaped to fit a certain type of creature's biology--a piece of leg armor for a standard bipedal humanoid is shaped to work with that skeletal structure & forward-jointed knee. Altering the size (specific dimensions) of Arcane Armor doesn't change the general shape that the armor takes. Arcane Armor shaped for a typical humanoid doesn't change shape to fit a bear.
You don't know what fear is until you've witnessed a drunk bird divebombing you while carrying a screaming Kobold throwing fire anywhere and everywhere.
They're not missing any.
Where are you getting this interpretation that arcane armor doesn't change it's shape to fit your body? Remember, arcane armor is not a regular piece of armor. If it was then your interpretation would be completely valid, but there is only one description of the armor's ability to change shape, and it states:
Nowhere in this description of the armor does it say the armor only expands to cover a specific, predefined part of your body. It says it expands to cover your entire body. A RAW interpretation of that is that it...well... expands to cover your entire body. This means if your body is a humanoid, it expands to cover your entire humanoid body. If your body is a bear, it expands to cover your entire bear body.
I could see a RAI interpretation limiting the ability of the arcane armor to cover your body if you wild shape into something really small (like an insect) or really massive (like an elephant), but RAW there is really nothing stopping druid from using arcane armor in wild shape.
I think the key point you're missing is that when you wild shape into an animal, you are no longer a humanoid. You are now the animal you wild shaped into. This means if you wild shape into a fish then you are not missing your arms and legs, because a fish does not have arms and legs. A fish is not supposed to have arms and legs, so when you are a fish you have all of your proper limbs.
You can't be missing something that you're not supposed to have, and because you're no longer a humanoid, you're no longer supposed to have humanoid limbs.
So, presuming that this works (considering the contention some have demonstrated, that is a big presumption), spending a bonus action to wild shape then an action to don the arcane armor, maybe we could take a moment to discuss the greater implications, both beneficial and potential pitfalls. Before that, one key point - armor doesn’t come as a suit. Breastplate doesn’t come with boots, nor gauntlets, nor a helm, not even pants (don’t know what you call armored pants). Therefore any of the aforementioned armor pieces are generated when the armor “expands to cover” the entire body. (Noted exclusions to the above statement include heavy armor and scale mail)
https://roll20.net/compendium/dnd5e/Armor#content
guardian armor - thunder damage gauntlets. If you shape change into a dire wolf, which while it doesn’t have hands, the armor will still expand over the paws. A reasonable dm may let you use the ‘gauntlet’ attack using paws. Also there is a bonus action that provides temp HP a certain number of times, no anatomical structure differences seem to restrict this.
infiltrator armor - sticking with the dire wolf example (though I encourage others to bring forward their own examples for discussion) the lightning launchers can be ‘gauntlet’ mounted or mounted on the chest (RAW). Reasonably it might be difficult for a wolf to aim a paw, which might cause someone to say the word dexterity, however all of the armorers arcane weapons use INT. To forego this argument simply mount the launcher to your chest (a listed option). I see no reason the advantage to stealth rolls wouldn’t also be in effect.
The following is the one major issue I see with this build; what happens to the armor when the wild shape is dropped, willingly or unwillingly? RAW, the best possible option I could see is that you could choose for the armor to fall to the ground. Either that, or it remains in the form it was in when you were wild shaped, potentially protecting you, but trapping you in place until you use an action to re-don the armor, or a bonus action to wild shape again. I say this since, as previously discussed, wild shape doesn’t cause the armor to change size and the arcane armor only expands to cover your entire body, it does not contract. If you have a forgiving dm they may allow you to revert to your normal form and continue wearing the armor “if your dm deems it reasonable.”
the above would be the best available raw potentials, though I certainly think the flavor of armorer, masters of their magic and craft, could do better. That kind of non-RAW is tap to DM specifications
Nowhere in the description of the armor does it say that the armor changes shape.
You have to be wearing the armor to begin with, so it has to start with the condition of armor that is shaped for your character's normal body type. Expansion is a function of size, not shape. Tailoring a shirt for perfect fit isn't a function of shape; the generic shape of a shirt for the human body remains the same, but the dimensions of the sleeve/cuff/neck/chest/shoulders are adjusted to perfectly fit your human body. The tailor isn't able to take a human shirt and adjust it to fit a bear.
The more I think about it, the more I think that I wouldn't allow my players to do this at all. I didn't think about the benefits of Armor Model, Armor Modifications, and Perfected Armor. None of this is meant to work with Wild Shape.
You don't know what fear is until you've witnessed a drunk bird divebombing you while carrying a screaming Kobold throwing fire anywhere and everywhere.
If we're going to get super pedantic with the words, keep in mind the description of the armor does not say that it expands to fit your body. It says the armor expands to cover your body. You do not need boots or a helmet to create the arcane armor (a suit of armor need not cover the entire body in order to be considered a suit), but the arcane armor does create these for you. This means if you use a suit of armor that does not include a helmet, or even if you use a suit of armor that has an open-faced helmet, the fact that the end result of the arcane armor covers your entire body means the armor must change its original shape. Even if the usage of the word 'expand' suggests it only changes size, the usage of the word 'cover' does suggest it changes its shape.
Also, the state of the armor when you create it does not matter, because the function of expanding to cover your body occurs any time you are wearing the armor, not just when you create the armor.
Whether or not the armor was meant to work with wild shape is also not really relevant. D&D (or literally any other game) is all about finding the creative solutions that perhaps no one else has thought of, as long as those solutions are not exploits (ie breaking the rules). The benefits of a player in wild shape using arcane armor really don't make that player more powerful than they could be with other multiclass options, nor do the benefits significantly outweigh the penalties a druid incurs by taking a minimum of 3 levels of artificer (or vice-versa, an artificer taking 2 levels of druid). There's no lore reason or game balance reason for arcane armor to not be used during wild shape, so the only argument left against it is whether or not it breaks the rules.
Like I said originally, this is indeed the prime question of whether or not arcane armor can be used with wild shape: Does the arcane armor expand to cover only the body you had when you first created the armor? Or does the armor expand to cover your current body? Nowhere in the rules is the first interpretation spelled out, and as I said before, there is a difference between armor changing to fit your body versus the armor changing to cover your body, so my interpretation would be that the armor expands to cover your current body, regardless of what your current body is.
Regardless, like so many other things in D&D, the fact that both of our arguments essentially come down to one or two word choices means that this a gray area, and so unless we receive a Sage Advice post on it, there will not be any single true answer. Your interpretation is just as valid as mine and if someone wants to create a druid/artificer multiclass with this feature in mind, they better make sure they talk to their own DM about it first, because regardless of our debate, that will be the only thing that matters.
You are right, it is a grey area. In fact, the wild shape rules even say it is up to the DM. All we know is that the default state of the game is that any particular piece of armor fits any particular humanoid character within reason, seemingly adjusting size to fit; It is explicitly stated that magic items automatically resize to fit; the armorer gains a similar ability allowing armor to expand to cover a character; and the Druid’s ability explicitly says that armor doesn’t change size to fit beast forms. Oh Yeah, and it is up to the DM to determine if a particular bit of equipment is reasonable for a beast to wear.
Edit: Oh, and there is a variant rule about equipment sizes.
Does this build straddle the fence as far as rules are concerned? Yes.
Would it be absolutely broken, especially if combined with a Kalashtar Bear Totem Barbarian? Yes.
Is it epic? Yes.
Would I allow it? No.
It would be particularly bad mixed with 3 levels of Barbarian, assuming you're answering the OP, who wanted to do this with ring mail a year and a half ago. Rage benefits don't apply in heavy armor. There's also nothing to straddle except for discussing whether or not Druids can wear ring mail, which we don't have any RAW clarification on - provided you remove that headache and discuss only armor the Druid will willingly wear, the only potential issue is whether or not the armor will change shape with the Druid, and that discussion can be avoided as well by choosing barding as the target armor to turn into Arcane Armor - e.g. for a Druid who habitually turns into a dire wolf, all you need is studded leather barding for a Dire Wolf and the only RAW concerns in this thread are rendered moot.