Magic item creation, mage armor x times per day

Question

Ok so I realize a +4 continuous armor enhancement like mage armor would cost 16k based on similar items. My question is this, what if the item created was a use per day item instead of continuous? For instance instead of a continuous effect the item in question could be activated x times per day for x number of hours. Looking at the dmg it seems this is doable but I am unclear as to how to price such an item. My assumption would be using the command word pricing spell level x caster level x 1800gp then divide by 5 for 5 charges per day. Is this reasonable or am I just cheating the system here?

Answer 1

We have several notable figures here:

• \$l_s\$, the level of the spell. Note that 0-level spells have \$l_s =\ \$½.

• \$l_c\$, the caster level of the spell; for a 1st-level spell this can be set to any value between 1 and the craft’s own caster level.

• 1,800 gp, the factor for command-word items.

• \$u_d\$, the number of times you can use it each day.

The formula these go into is

$$ l_s \times l_c \times 1\,800\text{ gp} \div \left(\frac{5}{u_d}\right) $$

This formula is from Table: Estimating Magic Item Gold Piece Values, specifically the Spell Effect and Special sections. Under Spell Effect we see command word defined as \$l_s \times l_c \times 1\,800\text{ gp}\$, and then under Special for charges per day we see “Divide by (5 divided by charges per day)” which is the same as “\$\div \left(\frac{5}{u_d}\right)\$.”

From here, we can manipulate the formula algebraically. Division by a fraction is the same as multiplying by its reciprocal (the same numbers “upside down”), so we can see this as this:

$$ l_s \times l_c \times 1\,800\text{ gp} \times \left(\frac{u_d}{5}\right) $$

Which simplifies to this:

$$ l_s \times l_c \times u_d \times 360\text{ gp} $$

Thus, for example, if you wanted to be able to use caster level 2nd mage armor (a 1st-level spell) 4 times per day (that is, \$l_s = 1\$, \$l_c = 2\$, and \$u_d = 4\$), we end up with

\begin{align} l_s \times l_c \times u_d \times 360\text{ gp} &= \\ 1 \times 2 \times 4 \times 360\text{ gp} &= \\ 2\,880\text{ gp} & \\ \end{align}

Because it has caster level 2nd, it lasts 2 hours each time it is used.

However!

It is very important to note that the item-creation guidelines are only guidelines, and the first guideline is always “compare to items with similar effects.” The bracers of armor +4 offer the same bonus continuously, but cost 16,000 gp rather than a mere 2,880 gp. Since 2 hours at a time is a good, long duration, and 4 uses per day is more than enough, 2,880 gp is too cheap for this item, no matter what the guidelines say. All custom items must be approved by the DM, and the DM is strongly encouraged to significantly increase the cost of this item.

Answer 2

The starting point for a command-word-activated, limited-use original magic item that creates an effect like the spell mage armor is not Table 7–33: Estimating Magic Item Gold Piece Values (Dungeon Master's Guide 285) but, instead, the magic item bracers of armor +4 (DMG 250) (16,000 gp; 0 lbs.). That's because Behind the Curtian: Magic Item Gold Piece Values, in part, says

Many factors must be considered when determining the price of magic items you invent. The easiest way to come up with a price is to match the new item to an item priced in this chapter and use its price as a guide. Otherwise, use the guidelines summarized on Table 7–33: Estimating Magic Item Gold Piece Values.

However, going from the bracers of armor +4 to using the table is a reasonable choice. This makes a command-word-activated cloak of mage armor (which, without the DM's intercession, would likely have a caster level of 7 as per the bracers) probably limited to a maximum of 2 uses per day. (More charges would see the new magic item's effects essentially last the whole day in which case the item should cost as much as the bracers.)

In this manner, the table estimates such a magic item's price at 6,400 gp. To this DM, that seem underpriced, and he might round up to 7,000 gp in a high-magic setting where a wearer that could afford the item could also reasonably see the effect dispelled in combat or nearly double the price to 12,000 gp in a low-magic setting where the PCs can be assured of sleeping regularly in relative safety.

Answer 3

You must note that having +4 AC isn't the same thing as having +X+4 AC (even if +X has its own cost, and especialy if that cost is very small). Just Armor bonus to AC (your item) is worse than Enhancement bonus to Armor bonus to AC (referred by item creation table). Or it is worse until its cost is way too low. It is your call to judge when "low" price becomes "too low", but it must be somewhere along the guidelines and maybe a bit more expensive. Certainly not as expensive as "Armor bonus (enhancement)".

As for command word (or use activated) charges per day type item, I think you should be consistent with your other rulings on item creation. In particular, you should increase its price if you are increasing the price of continuous item of this spell. Or you should increase prices of continuous items as a type. Still you have some room for fine tuning as nothing prevents it. Those two proposals are just examples of a good tone.

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As a side note, following the guidelines, the price for a command word item of Mage Armor with 5 charges per day would be:
(1 x caster level x 1800) / (5 / 5)
i.e. it equals the price for a command word item of Mage Armor with unlimited charges per day. And yes, you may consider changing only the price of "charges per day" modifier, for example. There is nothing wrong with it, as it is also only a guideline.