A device of this sort appears to be nothing but a cheap medallion or piece of valueless jewelry due to special enchantments placed upon it. 

If a character places it about his or her neck, however, that individual can see the necklace as it really is—golden missile globes depending from a golden chain. Each sphere is detachable only by the wearer. 

They can be easily hurled up to 7" distance. 

When they arrive at the end of their trajectory they burst as a magical fireball. 

The number of missiles, and their respective hit dice of fireball damage, are determined on the table below:

For example, on a roll of 9-12 the necklace will possess 7 missiles—one 7-dice, two 5-dice, and four 3-dice fireballs.

The size will show that there is a difference in power between globes, but the number of dice and damage each causes cannot generally be known.

If the necklace is being worn or carried by a character who fails his or her saving throw versus a magical fire attack, the item must undergo a saving throw check as well. If it fails to save, all remaining missiles detonate simultaneously.