In chat I learned that failing a saving throw against a spell can potentially damage worn equipment: "If a creature rolls a natural 1 on its saving throw against the effect, however, an exposed item is harmed (if the attack can harm objects)."
But how does one determine if a spell can damage objects?
Examples
- The spell shatter has (object) in its saving throw entry, so it can be cast on objects and, therefore, damage objects.
- The spell fireball says it damages objects.
- The spell cone of cold does not say it damages objects, but it is an area spell that deals energy damage (i.e. acid, electricity, fire, sonic, and, in this case, cold) and, as such, has specific rules.
- The spell flame strike does not say it damages objects, and it, too, is an area spell that deals energy damage, but also half the spell's damage is divine rather than energy.
- The spell chaos hammer is described as "a multicolored explosion of leaping, ricocheting energy," but it does not technically deal energy damage.
- The spell slay living has as its target living creature touched so it shouldn't damage objects.
Related question include Do area of effect spells damage objects? (about 3.5e's cone of cold), Kill with magic = destroy carried items? (about worn items damaged by spells without saving throw), and Did my clothes catch fire? (about damaging clothing), but none address this issue specifically with Pathfinder in mind.
Best Answer
In this GM's opinion, a spell's description provides the only guidance for determining if a spell that has an Area entry that also deals damage also deals that damage to objects within that area.
That is, while Damaging Objects on Saving Throws on Attended Items does say, "Unless the descriptive text for a spell (or attack) specifies otherwise, all items carried or worn by a creature are assumed to survive a magical attack," on Unattended Items says, "Non-magical, unattended items never make saving throws. They are considered to have failed their saving throws, so they are always fully affected by spells and other attacks that allow saving throws to resist or negate," but when taken together it's unclear if this means either All items not carried or worn by a creature are assumed to be dealt damage by effects that affect an area or A spell (or attack) will specify that items not carried or worn by a creature are dealt damage by effects that affect an area.
While this answer gravitates toward All items not carried or worn by a creature are assumed to be dealt damage by effects that affect an area, in this GM's campaigns A spell (or attack) will specify that items not carried or worn by a creature are dealt damage by effects that affect an area. A reader may judge me lazy, but I just don't want to track damage to unattended objects (and have that matter) if I don't have to. I feel there are better ways for a GM to spend his time. To that end, to determine if a spell deals damage to unattended objects in its area, I use as a guideline a really strict reading of those 40-year-old standbys, the spells fireball and lightning bolt.
Bear with me here. The spell fireball says that
(Emphasis mine.) Similarly, the spell lightning bolt says
(Emphasis mine.) Some will be quick to point out that just because, for example, the (equally elderly) spell flame strike does not say it deals damage to unattended objects in its cylinder also does not mean it doesn't deal damage to unattended objects object in its cylinder. But, because—unlike fireball and lightning bolt—there are no specific rules for what happens to a barrier when part of a flame strike's effect intersects with it, this GM has the flame strike spell stop at the barrier just as any other spell effect does and leave the barrier undamaged. That's just how I roll. (As the spell flame strike has as its area a cylinder, its effect usually ignores obstructions, but this GM would not let a flame strike spell ignore, for example, a wall of stone spell that'd been cast to form a dome above creatures in the flame strike's area!)
This ruling does lessen the danger of the natural-1-on-a-saving-throw-and-see-an-item-damaged rule, but this GM is comfortable with that, viewing that particular rule as a throwback to the hoary days of insult-to-injury Gotcha! DMing anyway.
That said, in my campaigns here's how the examples work.
The spell shatter, when it's used—as described in its second paragraph—as an area spell
However, according to the spell's second saving throw entry, a creature in the area that's attending objects that such a shatter could affect makes a Will save to negate the spell's effect. Yet all of a creature's attended items are affected if the creature either fails the Will saving throw or rolls a natural 1 on the Will saving throw, so, ultimately, it doesn't matter, the results of either being identical. (This GM would have an appropriate magic item possessing a higher Will saving throw bonus than the attending creature make its Will saving throw separately. Then this GM would chide that creature for have a weaker will than its magic items.)
I should note that the alternative gets messy. For example, not only will a warrior find his tower shield (that most portable of barriers—no matter how ill-advised) dissolving under assaults that would've previously left it unharmed (having, after all, only hardness 5 and hp 20), but also remember that areas are usually solids not planes, even though they are often represented as planes for convenient grid placement. That means casters must become extremely cautious or find their spells destroying the very structures on which they're fighting, and dragons must be wary lest their breath weapons collapse their own lairs! That is, the alternative would see every 5-ft. square of terrain in an area dealt damage, and that damage may destroy the very adventure site, not to mention, inadvertently, the party!
So that's this GM's standard for whether or not a spell affects objects, unattended or not and area spell or not. I'm not, like, utterly inflexible on this, though. For example, because a ray is like "using a ranged weapon," such a spell could be directed at anything (including objects or the darkness), and the spell'll affect objects appropriately (e.g. the spells scorching ray and polar ray as ranged energy attacks deal one-fourth or one-third damage to objects, but most objects will be unaffected by the spell ray of enfeeblement). However, a caster that wants, for example, a spell like cone of cold except that it also damages objects in the area like fireball (only, y'know, in a cone and with cold) would have to research and design that spell.