How should the price, hit point and hardness (and aura) be calculated for a magical weapon & armor shield?

Question

The core rule mentioned that each enhancement bonus granted to a weapon/armor would also grant it additional hardness and hit points.

It also mentioned that while shields can be enchanted as armors, they can also be made magic weapons.

So if there's a shield, being enchanted to be +5 shield as an armor (+40000gp) and also being enchanted to be a +5 shield as a weapon (+80000gp), would its price be its original price +120000gp? Would the hit point and hardness improvement conflict with each other? If NPCs see it with detect magic, would they see it as a +5 item or something much stronger than that (perhaps a +10 item)?

Answer 1

You're basically on the right path, but your numbers are off.

To calculate shield price, start with a masterwork shield: 159 for a masterwork light steel shield. Then add the cost of the shield enchantment (5^2 * 1000 = 25000).

You can arguably target a regular shield for weapon enchantment, but it's unclear. You can definitely target a spiked shield though:

An enhancement bonus on a spiked shield does not improve the effectiveness of a shield bash made with it, but a spiked shield can be made into a magic weapon in its own right.

That works essentially the same way as above. Shield spikes, 10 g. Masterwork quality, 300. + 5 enchantment, (5^2 * 2000 = 50,000).

So all together, that shield costs 75,459 gold.

---

Aura strength is based on caster level. See the detect magic spell.

---

Item hp and hardness usually don't matter. But it's easy enough to find: the base value is 10 hp and 10 hardness for a small steel shield. Then,

Each +1 of enhancement bonus adds 2 to the hardness of armor, a weapon, or a shield and +10 to the item’s hit points.

You have two different +5 enhancement bonuses on your shield so it would be hardness 30 and 110 hp.

Finally, your question suggests that you're not sure what hardness is:

Each object has hardness—a number that represents how well it resists damage. Whenever an object takes damage, subtract its hardness from the damage. Only damage in excess of its hardness is deducted from the object’s hit points

(All quotes via d20srd.org)

Answer 2

A +5 enhancement to a shield-as-armor costs 5² × 1,000 gp = 25,000 gp, not 40,000 gp.

A +5 enhancement to a shield-as-weapon costs 5² × 2,000 gp = 50,000 gp, not 80,000 gp.

I have no idea where you got 40,000 gp and 80,000 gp from, but they are incorrect.

Anyway, both of these kinds of enhancements can be applied to a shield:

An enhancement bonus on a shield does not improve the effectiveness of a shield bash made with it, but the shield can be made into a magic weapon in its own right.

Unfortunately, aside from the statement that it can be done, we have no rules for how it actually works—which is to say, we don’t get explicit rules telling us how much it costs.

For instance, does the shield have to be a masterwork weapon as well as a masterwork shield? That would cost 300 gp, but it’s not clear if it’s necessary.

Furthermore, combining magical enhancements together can—in the context of worn magic items using body slots, not in the context of a held item like a shield—cost 50% of the lesser-valued cost extra. Does that apply here? RAW, no, but a lot of people suspect that it maybe is supposed to.

There just aren’t answers to these questions to be had.

But for my money—and I do know a lot about this system—the answer is simply “price a magic shield and a magic weapon independently of one another, and pay both costs—those payments just happen to be going towards one item that does both things rather than two separate items.” So, say, a +5 heavy steel shield that is also a +5 shield-bash costs

20 gp [base cost of a heavy steel shield]
+ 150 gp [mwk. armor] + 25,000 gp [+5 armor]
+ 300 gp [mwk. weapon] + 50,000 gp [+5 weapon]
= 75,470 gp

You can avoid all of the uncertainty behind this—and get a damage boost, to boot—by using 10-gp shield spikes. Then you clearly spend 20 gp + 150 gp + 25,000 gp = 25,170 gp for your +5 heavy steel shield and 10 gp + 300 gp + 50,000 gp = 50,310 gp for your +5 shield spikes as separate items that happen to live together on the same physical object (that is worth 75,480 gp). My above calculation assumes that things for the un-spiked version should be the same, just without the 10 gp for the shield spikes themselves.