The Spell Armor (Unearthed Arcana p.51-52) states:

The caster creates ,a magical field of force which serves as if it were leather armor (AC 8). If the spell is cast upon a person already armored, it has no effect. However, if it is cast upon a creature with an armor class normally better than 9 (due to its size, speed, skin, etc.) it will benefit the normal armor class by one step, i.e. AC 8 becomes 7, AC 7 becomes 6, and so on. The magic armor spell does not slow or hinder movement, adds no weight or encumbrance, nor does it prevent spell casting(...)

Normally,a character with 16 dex + a leather armor would have AC 6, what bugs me is the ''etc.'' in the examples, I believe it is fair to say that my magic-user would have AC 6 since a comparison can be made with the real armor that it imitates, and ''etc.'' might be other examples that I'm not aware of, but I don't think the AC from dexterity is included in those examples unless ''speed'' means dex.

In the player handbook the description of Dexterity states:

Dexterity encompasses a number of physical attributes including hand-eye coordination, agility, reflexes, precision, balance, and speed of movement. A high dexterity indicates superiority in all of the above attributes(...)

So perhaps speed means Dexterity?

The spell Find Familiar also states:

Normal familiars have 2-4 hit points and armor class of 7 (due to size, speed, etc.)

So is speed just a synonym for a high dexterity score? Is there another spell (Haste does not) or buff or mention of a rule somewhere that shows a distinction between ''speed'' and ''high dexterity''?

In short:

Is my AC 6 or 7? in this case what does ''speed'' refer to?

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    \$\begingroup\$ No, speed does not mean dexterity. Speed is related to movement rate in inches (typically 12 for a PC). You will note that you get no movement rate change on the dexterity table. It's more an abstraction, but we did use dexterity as a comparative stat if one was in a foot race ...but on the other hand, the way that AC is assigned in 1e in the MM is sometimes arcane and hard to fathom, between speed and armor skin type and so on ... \$\endgroup\$ Mar 19, 2020 at 12:15
  • \$\begingroup\$ You can say that dexterity is "speed" in a narrative sense, not a mechanical sense. Beyond that, krb has the right of it. \$\endgroup\$ Mar 19, 2020 at 12:21
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    \$\begingroup\$ For a PC, it does not. They are using the term "speed" descriptively and narratively, not mechanically. For practical in game movement, you use the movement rate in inches from the MM for monsters. See Encumbrance and Movement on PHB pages 101 and 102. \$\endgroup\$ Mar 19, 2020 at 13:58
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    \$\begingroup\$ And for what it's worth, I wish they'd have used the term 'quickness' rather than 'speed of movement' in that description of dexterity scores, which is just above the table. Quickness better reflects the bonuses for reaction and armor class that are in the table .... but I didn't write the PHB, so we get to try and parse Gygaxian English usage. That became for us a sub hobby of the D&D hobby when the AD&D books came out ... \$\endgroup\$ Mar 19, 2020 at 14:15
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    \$\begingroup\$ Not only does trying to understand the term speed lead to confusion, it leads to this question being off topic for this stack. The Monster Manual generally does not explain how a creature attains the AC rating that it is given. Some are being small and hard to hit. Some move quickly, like a bird or a snake. Some have very thick hide or armored scales. But the descriptions don't give us an explanation of why the game creators assigned the indicated armor class. Trying to decrypt their logic for assigning an AC to a creature makes this a question about "author intent." \$\endgroup\$
    – krb
    Mar 19, 2020 at 19:53

2 Answers 2


The spell says "functions as leather armor" so you cannot go wrong by doing what the description says and treating it as leather armor, giving you AC8 before applying adjustments from DEX.

You don't mention the race of the character, but all of the usual suspects (human, elf, dwarf, etc.) have a base AC of 10. Individual specimens might have an adjustment to their AC based on DEX or other factors, but the base AC of all members of the race is still a 10.

  • \$\begingroup\$ I edited and added that I was human. and by RAW only human,elf or half-elf can be magic-user. and when the rule mention ''speed'' such as in Find Familiar it says: Normal familiars hove 2-4 hit points and armor class of 7 (due to size, speed, etc.). what does ''speed'' refer to? isn't it dex? can you give me more details on this please? \$\endgroup\$ Mar 19, 2020 at 6:00
  • \$\begingroup\$ So far as I can recall, speed is not a property of characters or of creatures. There is movement rate which is based on race/creature type and there is reaction adjustment which is based on DEX. The only official use of "speed" that comes to mind is weapon speed and that does apply in this context. \$\endgroup\$
    – krb
    Mar 19, 2020 at 19:29
  • \$\begingroup\$ If you could add the tiny bit about the MM not explaining where the AC comes from and that it does not apply to players, I'll upvote (need an edit anyways) and chose this as the answer. please I believe it will help the community. \$\endgroup\$ Mar 20, 2020 at 6:25
  • \$\begingroup\$ @krb: if you wish, you can see my comments under the other answer for DMG references that may better support your answer. (AC 6 is the correct answer). DMG p 28 has the details. \$\endgroup\$ Mar 24, 2020 at 12:50

Unhelpful, I know, but I'm going to differ. I would hold your MU has AC7. Here's why, and I'll take the clause by parts:

However, if it is cast upon a creature with an armor class normally better than 9 (due to its size, speed, skin, etc.) it will benefit the normal armor class by one step

Cast upon a creature: looking through the MU spells for other uses of the term, I quickly find Feather Fall ("the creature(s) or objects affected", and I've never heard it suggested you can't use FF on a PC, including oneself), Message ("the creature who received the message can whisper a reply", and I've not heard it suggested Message can't be used between two party members), and Levitate ("the magic-user can place it upon ... some other creature", and party members regularly get levitated), to name but three. So I see no reason to think that the term creature is normally used in spell descriptions to implicitly exempt either party members or the caster him/herself.

with an armor class normally better than 9: your MU has a DEX of 16 and no other items that would affect armor class (that we are told of), so has AC8, which is better than 9. As for "normally", DEX is not something that may be deactivated or laid aside, but is an ability possessed 24*7; I can't think of circumstances more normal than those which always apply. I agree that humans en bloc have a normal AC of 10, but the text reads "a creature with an AC normally better than 9", not "a member of a race with an AC normally better than 9". The evaluation to be made is of the creature itself, not its family, friends, nor any other examples to hand.

due to its size, speed, skin, etc.: the presence of "etc." indicates to me that the list is not intended to be exhaustive, but instead contains examples of factors that give rise to a "normal" AC. I agree an interesting discussion may be had about whether DEX bonuses constitute speed, but it's not necessary to have it here, as the list is not exhaustive. Instead, the list trammels up all reasons why a creature's AC may normally be better than 9.

I reject my learned colleague's analysis, which turns on the phrase "functions as leather armor" to justify treating the result as if a suit of leather armour had popped out of thin air, since the spell promptly lists many other reasons why its effect is not identical to simple leather armour ("does not slow or hinder movement, adds no weight or encumbrance, nor does it prevent spell casting").

This given, I would hold that the clause quoted above does apply to your MU, and so (s)he acquires AC7 when the spell is cast.

  • \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$
    – V2Blast
    Mar 24, 2020 at 20:58
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    \$\begingroup\$ Nice points but I've read the discussion and I my DM did agree it was now AC6. AD&D 1e does mentions a few times in the PHB ''refer to your referee'' so I guess both answers are good in this edition, but since you can lose your dex bonus, it is better for it to be always -1 or always -2 not depending on being ''flat footed'' (depends if you have hard skin etc.) and no info is really available in 2020 for the speed confusion, so rule it however you want, both are ok. but makes more sense for it to be -2 if only dex is the factor for the question. \$\endgroup\$ Mar 26, 2020 at 14:55

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