I want one of my NPCs to have a custom Ioun stone:
Ioun stone, dark galena
Aura moderate evocation; CL 12th
Slot none; Weight —.
With a command word, the user may activate or de-activate the fast-spinning mode of this stone. When in its fast-spinning mode it tries to hurt people who stands close to the owner: Each turn, the stone attacks one adjacent creature, chosen at random, using the BAB + mental ability modifier of the owner (the mental ability used is chosen when each Ioun stone is created). If it hits, the stone deals 1d4 bludgeoning damages.
The owner's mount and any creatures carried by the user are excluded from potential targets.
The stone stays in its fast-spinning mode until it is de-activated or separated from its owner.
The stone can be targeted as a normal piece of equipment by maneuvers. A creature attacked by the stone gets a +2 circumstance bonus to its CMB during the next turn for steal or sunder maneuvers that target the stone.
There's capacity for these specific Ioun stones to stack if you have several, and that's intentional.
I am looking for a price that would be fair for such an item. I am thinking about 5,000 gp.