So, my group is about to fight a nightwalker. I looked through its stats, and it seems to be really good at sundering. Now, I can easily look up the hardness/HP of weapons for the purpose of sunder, but virtually none of my PCs have weapons (they're all casters).

So, my question is this: What's the hardness/HP of a headband of +stat? What's the hardness/HP of a cloak of resistance+5? Is there a centralized location that answers the hardness/HP question, or do I just try to guesstimate it based on the substance hardness chart?

The description on +stat headbands say they're silver, but substance hardness doesn't have silver. I'm thinking of assuming steel hardness, but I still don't really know how thick they are. And if cloaks of resistance have 2hp and 0 hardness, then why don't they just get sundered every combat?

Magic items, unless otherwise noted, take damage as nonmagical items of the same sort. A damaged magic item continues to function, but if it is destroyed, all its magical power is lost. Magic items that take damage in excess of half their total hit points, but not more than their total hit points, gain the broken condition, and might not function properly.

Most magical items are just as easy to destroy as a mundane item.

Potions: The vial has AC 13, 1 hit point, hardness 1, and a break DC of 12
Rings: A ring has AC 13, 2 hit points, hardness 10, and a break DC of 25.
Rods: These sturdy items have AC 9, 10 hit points, hardness 10, and a break DC of 27.
Scrolls: A scroll has AC 9, 1 hit point, hardness 0, and a break DC of 8.
Staves: It has AC 7, 10 hit points, hardness 5, and a break DC of 24.
Wands: A typical wand has AC 7, 5 hit points, hardness 5, and a break DC of 16
Magic Armor, Shields, and Weapons: 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.

So for wondrous items, just give them from 1-10 hitpoints, and an appropriate hardness.

The description on +stat headbands say they're silver, but substance hardness doesn't have silver. I'm thinking of assuming steel hardness, but I still don't really know how thick they are. And if cloaks of resistance have 2hp and 0 hardness, then why don't they just get sundered every combat?

The alchemical silver material is listed as Hardness 8 and 10 hit points per inch, so regular silver should be the same or somewhat less.

As for why they usually aren't in combat? Most magical items aren't obviously magical. Why take the time to just randomly attack someones (potentially mundane)cloak, instead of attacking the person themselves?

All of my questions are completely answered. Thank you!

Last question first - why don't they get sundered every combat? Because they're treasure! Monsters certainly plan on taking the stuff from dead adventurers.

As for silver, it's softer than steel, of course - in "real life" - but for game purposes I'd probably just call it 10. It's pretty thin - it's a headband - so probably I'd give it 5 hit points (1/6" thickness). Now, magic armor grants hardness 2 and 10 hit points per +1 enhancement bonus, but it's extremely arguable whether a headband is "armor like" or a headbands enhancement bonus akin to an armor's enhancement bonus. I tend to say "no"... but on the other hand, 5 hit points and hardness 10 is pretty low (nevermind the absurdity of sundering a headband without injuring the wearer!)

But, if we did decide, as a GM, to be merciful, we could say that a +2 headband has hardness 14 and 25 hit points, and a +6 headband would have 22 hardness (harder than adamantine) and 65 hit points. Again, I say "no, I don't think so", but it's there as an interpretive option.

With a cloak, we could again make the same argument, though the notion of a+5 cloak having hardness 10 (wears like steel!) and 52 hit points seems... silly.

But yes, the secret to terrifying adventurers with a nightwalker is to destroy their stuff - it's what they do (though the 3.5 nightwalkers were even worse... they autodestroyed items). Between that and a CL16 greater dispel magic at will (lol buffs), they're tres nasty.

Edit: Ninja'd, I see :) Good point on alchemical silver - hardness 8. Quick snacks for a determined nightwalker.