The Flaming Sphere spell states that "It ignites flammable substances it touches and illuminates the same area as a torch would."
So if a Flaming Sphere rolled into or through a square that had a Fuse Grenade in it, would the sphere ignite the grenade's fuse? (my gut reaction: yes) Furthermore, if a character in the same square as a Flaming Sphere were to pull out a Fuse Grenade, would the grenade _automatically_ light, or would you still make the character spend a move action to light the fuse? (I want to say it's a free lit fuse, but I'm biased)
FYI, I'm running the Ironfang Invasion campaign (first time as DM in pathfinder), and I'm dying to have my hobgoblins use the Sting Grenade, but it just takes too long to pull one out, light it, and throw it to make it worthwhile. However, the party has a character who keeps using flaming spheres to make my life difficult and they're going to be going up against a group of hobgoblins for a rematch fight (at Camp Redjaw - party had to withdraw from the first assault), so I figured it wouldn't be too cheesy for the hobs to be waiting around with sting grenades at the ready - they've already seen the flaming sphere once, so they'll prep for it for the second encounter.
PS - for extra fun, what if you had a hobgoblin wearing a bandolier with 3 fuse grenades in it, and it gets hit by a flaming sphere - all three fuses lit? Heh heh heh...
Well, they might ignite, but then again the whole thing should also take the fire damage, which should probably cause it to explode on the spot.
That's the problem with these sorts of things, it could be interpreted a lot of ways.
Go with a ruling that is unlikely to cause your players to be upset or be able to be abused by them in the future.
Good answer - thanks. Didn't think of item damage from the sphere.
Hardness of a clay pot designed to not break when thrown? I wouldn't want to call it stone (hardness 8), so perhaps something more like wood is the appropriate comparison. So Hardness 5, and for a 1/2" thick at 10 hp / inch, 5 hit points? These are key assumptions.
3d6 fire damage gives an average roll of 10.5, half damage for elemental damage vs. object, gives about 5 points of damage for the average roll, which is negated by the hardness. So the average roll would do no damage to the fuse grenade.
To put it another way, with hardness 5 and 5 hp, the fire damage roll would have to be 20 (20/2 = 10, 10 - 5 hardness = 5 hp damage), which is impossible with a single 3d6 roll. If you gave the pot had 4 hp it would be possible on a roll of 18 (1 in 216 chance), or 3 hp would make it possible on a roll of 16 (10 in 216). If you lowered the hardness of the clay pot to 4, then it would be possible to destroy a 5 hp pot on an 18, a 4 hp pot on a 16. Still pretty low odds.
"Go with a ruling that is unlikely to cause your players to be upset or be able to be abused by them in the future."
Solid advice. My players have a strong bent for power gaming and are on the hotheaded side. Sometimes they really surprise me on what they get angry about.
Ah, a better estimate on clay:
masonry wall, hardness 8, 90 hp / foot of thickness, which is 7.5 hp / inch.
So if bricks are hardness of 8, then clay pots should be similar. A half inch thick pot should have about 3.75 hp, so we'll round that up to 4. Thus it takes (4 + 8) * 2 = 24 hp of fire damage to ruin a 1/2" thick clay pot, which is impossible in a single round for a flaming sphere; with a hardness of 8 the highest damage it could do is 1 hp on a roll of 18.
Done. The fuse grenade (and it's variants) are effectively indestructible by a flaming sphere (which makes some sense as the clay was already fired at what temperature? pretty damn hot), but the fuse lights.