My party is working on a plan to take out an unusually difficult monster by luring him into an enclosed area and detonating an entire Necklace of Fireballs (Type II) at once under his feet.
The plan works something like this:
1) The wizard in the party goes invisible and casts fly.
2) He plucks the 6d6 sphere from the necklace.
3) He takes off the necklace and hands it to an Unseen Servant.
4) The Unseen Servant takes it ahead into a tunnel.
5) The wizard blows a signal whistle to attract attention.
6) When the monster comes, the wizard throws the 6d6 sphere at the necklace and flies away, thereby leading the monster (if it survives the initial blast) to an ambush by the rest of the party.
There may also be some caltrops and bear traps involved.
Anyway, I figure there are two ways this plays out. If the necklace fails its save (DC 14, +7 bonus), it detonates. But if it succeeds on its save, it only detonates if it takes enough damage to destroy the necklace.
A successful save halves the damage to start with, and objects generally take only half damage from energy attacks anyway (p. 173 in Additional Rules), so on a successful save it only takes 25% of the damage from the 6d6 sphere.
So the question is -- how many hit points does a Type II Necklace of Fireballs have?
As jewelry, it's probably made of either gold or silver, but I haven't found hardness/hit point figures for either of those materials. And it probably gets some kind of hit point bonus for being magic -- at any rate magic weapons and armor do, but I haven't found any rules for other types of magic items.
Thoughts?
