Can an Armorer Artificer wear another set of armor with their Arcane Armor?

Question

The Arcane Armor feature from the Armorer subclass has the following line:

“The armor continues to be Arcane Armor until you don another suit of armor or you die.”

If an Armorer Artificer is wearing two sets of armor that can logically be worn with each other (like say Molten Bronze Skin and Efreeti Chain), and they then designate one of the sets of armor that they’re wearing as their Arcane Armor, can they still wear both suits of armor given that they haven’t donned any armor while wearing their Arcane Armor?

Answer 1

The intent is obvious: you cannot wear Arcane Armor and another suit of armor.

The rules for “Multiple Items of the Same Kind” state:

A character can’t normally wear more than one pair of footwear, one pair of gloves or gauntlets, one pair of bracers, one suit of armor, one item of headwear, and one cloak.

The rules for Arcane Armor are written with this in mind - you can only wear one suit of armor. So it is entirely natural that the rules would not address what happens if you are already wearing two sets of armor when you convert one to Arcane Armor: you aren’t supposed to be wearing two, so there’s no need to explain what happens when you are. So if we have an unusual exception to the general rules, like you happen to be wearing two armors at once somehow, we shouldn’t be surprised when strange things happen or the rules become muddy.

So yeah, if you want to be pedantic in your rulings, you can use this as a work around as the strictly technical reading allows you to do this, but the intent is abundantly obvious: it doesn’t work that way. To be clear, there is nothing inherently wrong with being pedantic in your rulings, I’m quite proud of my most downvoted answer. Just make sure you talk about it with the table if you are going to insist on using a ruling that is quite obviously against the intent of a feature. And if you are not the DM, don’t get upset when they rule that your idea doesn’t work.

Answer 2

Per the DMG:

Use common sense to determine whether more than one of a given kind of magic item can be worn. A character can’t normally wear more than one pair of footwear, one pair of gloves or gauntlets, one pair of bracers, one suit of armor, one item of headwear, and one cloak. You can make exceptions; a character might be able to wear a circlet under a helmet, for example, or be able to layer two cloaks.

So you cannot wear two types of armor at the same time. Although a DM may say that you can wear two armor-like things at the same time; like a magic helm and magic boots.

Also, per the description of Molten Skin:

When you attune to it, the bronze adheres and contours to your skin. The armor can be worn under normal clothes, but it doesn't impede bodily functions.

It specifies it can be worn under clothes, but does not say it can be worn under other armor. Mithral armor also has a similar clause:

A mithral chain shirt or breastplate can be worn under normal clothes.

---

So, let's say you find a DM that lets you wear two armors at once

What do you hope to gain by this?

Using your example of Bronze Skin (Plate) and Efreeti Chain:

• Both have weight and encumbrance. For this example you're at 120 lbs worth of armor.
• You can only have one formula for figuring out AC. So it's either 19 for Efreeti Chain (AC 16 + 3) or 18 for Molten Bronze Skin (AC 18).
• The skin gives the wearer fire resistance. It doesn't impose Disadvantage on Stealth, but you need at least a 15 Strength or else suffer a movement penalty. Unless this is your Arcane Armor so no requirement.
• The chain give IMMUNITY to fire damage so much better than the skin. Now you DO have Disadvantage on Stealth, and this armor still has a 13 Strength requirement. Oh, and you can also talk Primordial and walk on lava.

So in most every way, just wearing the Efreeti Chain is better by itself without having to apply Bronze Skin first. And congrats on getting a legendary item and feeling the need that it's still not enough armor.

What I think you are asking for

The only reason for all of this shenanigans is so that you can wear the skin when there are times you cannot wear the chain.

• Diplomatic meeting where the character wants to appear unarmed
• Stealth missions (to remove the disadvantage)
• Sleeping, bathing, or during times of "bodily functions" as the Molten Skin description puts it
• The Chain is a secret (don't want certain people to know that you own it/wear it)

Or you think you always need to have Arcane Armor available. But here is all that gets you:

• If the armor normally has a Strength requirement, the arcane armor lacks this requirement for you. (So if you're wearing just Chain, you don't even need Strength 13)
• You can use the arcane armor as a spellcasting focus for your artificer spells. (Can. You can still use Smith's Tools for spell casting)
• 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. (Are you missing any limbs that need to be replaced that a Regeneration or Wish spell couldn't handle?)
• You can doff or don the armor as an action. The armor continues to be Arcane Armor until you don another suit of armor or you die. (This is odd and I'll cover it at the end)
• Has built-in weapons, Thunder Gauntlets or Lightning Launchers, that get better at higher levels. (Just keep a normal weapon handy)
• More infusions. (It's still Arcane Armor if you take it off so unless the Infusion is required for living, I don't know what to say)

In which case, a simpler solution would be Mage Armor and a Ring of Fire Resistance.

• The Mage Armor spell is first level so it can be cast by a friendly Wizard or Sorcerer. If you're a Hexblade is is also available as an Invocation. It's 8 hours of AC 13 + Dexterity (which is probably small considering you prefer Heavy Armor, but it's still a factor). Maybe someone can load up a Ring of Spell Storing with five doses and you only use it when required?
• The Ring of Fire Resistance will give the same resistance as the skin, also doesn't effect Stealth, uses the same Attunement slot as the skin, and as a bonus, doesn't care about your Strength.

Answer 3

Can't Wear Two Sets

Can't wear two sets of armor according to the rules of magical items.

A character can't normally wear more than one pair of footwear, one pair of gloves or gauntlets, one pair of bracers, one suit of armor, one item of headwear, and one cloak.

Would Only get AC from One if you Could

Sage Advice makes clear you can only use one formula for calculating your AC at a time.

These methods—along with any others that give you a formula for calculating your AC—are mutually exclusive; you can benefit from only one at a time. I

The Molten Bronze Armor is one way.

Breastplate 14 + Dex modifier (max 2) Half Plate 15 + Dex modifier (max 2) -- -- Plate 18

Normal armor is another, and Efreeti Chain +3 is Heavy Chain so it would use this formula:

Chain mail 16 [+3 from Efreeti Chain]

So, Molten Bronze Armor Plate would be 18 and Efreeti Chain would be 16 + 3 = 19. You can choose to take the 18 or the 19, but Rules as Written, you can't do 18+3.

Arcane Armor Only Works on One Anyway

If you could wear two sets, you could turn either into Arcane Armor, but not both. The lines here clearly assume one set of armor, because that is what the rules dictate.

As an action, you can turn a suit of armor you are wearing into Arcane Armor, provided you have smith’s tools in hand. ... The armor continues to be Arcane Armor until you don another suit of armor or you die.

Assume you Could... Benifit?

For the sake of argument and completeness, let's assume your DM allows it, despite being against rules as written.

• If the armor normally has a Strength requirement, the arcane armor lacks this requirement for you.

Shouldn't be a big deal. Chain doesn't have strength requirement. You'd just make the Bronze Skin the Arcane Armor because it has a strength requirement. Having both doesn't gain you anything.

• You can use the arcane armor as a spellcasting focus for your artificer spells.

You already have one arcane armor and the tools, so gaining another focus isn't a benefit after the first.

• 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.

Small to no benefit to having the outer layer unremovable also if it doesn't protect the +3, because the AC would still either be the 16 or the 18; you simply can't do the 21 by RAW anyway. So making the molten bronze skin the Arcane Armor still makes more sense. How often are your party stripped of their armor?

• You can doff or don the armor as an action.

How often do get naked in battle? Donning the armor quickly would be nice but is there a reason to ever take the molten bronze skin off anyway?

Answer 4

Possibly, but I wouldn't allow it.

As you said, Arcane Armor stops being arcane armor if you put on another suit of armor (or die).

Technically speaking, in the scenario you describe, you aren't donning any armor after the Arcane Armor, so you haven't run afoul of the exact wording of the class ability. However, I think this is pretty clearly against the intent that your arcane armor is your one and only armor. "The artificer bonds with this armor, becoming one with it...", and they included a specific rule that you can't even put on a different suit of armor without screwing up that bond.

The flavor and design of the class are that your Arcane Armor is special, so bypassing that by slipping around the exact language is just cheesy. As a DM, I wouldn't allow you to do this.