I have a player giving me a real hard time for targeting his Rune Stone during combat with a CR 13 Mummy Monk. He did a flurry of blows and 2 of the 6 went to the stone. He thinks no monster/opponent would ever target the stones. Are the stone a viable target during combat?
I would say it depends on the intelligence of the enemy, and if they would recognize what the Rune Stone is.
This also falls into the same realm as Sundering gear. It can be done, it might be a good tactic for an enemy, but a lot of players are pretty unhappy about it.
Most bad guys try to kill or otherwise incapacitate you, not piss you off at the expense of their own lives. Sundering armor, weapons, or the wand that maniacally-cackling wizard is waving around--these are viable tactics as they increase the sunderer's likelihood of winning the battle. Sundering a runestone of power (I assume that's the item in question) doesn't really do much other than make the sorcerer (and her player) angry.
Viable target, yes. Would the mummy target them? Maybe, it's really hard to say. If the mummy somehow recognized the caster using the stone(s) it might reason out that the caster is using the power of stone for extra spells. However, without having previously seen a runestone or understanding what it does (or might do) it seems unlikely.
Did the caster use more than one stone in that combat? Could the mummy have used knowledge(arcna) or spellcraft to possibly identify the item before use? If the answer to both of these is no, it seems unlikely the mummy would be aware of the benefit of the stone and target it.
I have a player giving me a real hard time for targeting his Rune Stone during combat with a CR 13 Mummy Monk. He did a flurry of blows and 2 of the 6 went to the stone. He thinks no monster/opponent would ever target the stones. Are the stone a viable target during combat?
The Rune Stone is an Ioun Stone
Oh. Well, yes, that may be viable tactic for a moderately intelligent enemy It doesn't take a lot of brainpower to realize that the magic crystal thing revolving around your head might be somehow helping you. It'd be easier to just grab it instead of sundering it, though, unless your hands are full. (Given the way the rules are written there, I'd rule that a successful hit would swat the thing away even if it didn't bypass hardness.)
I'm pretty sure runestones aren't ioun stones, unless you meant ioun stone originally instead of runestone.
Runestone's of Power (Runestone for short) are the equivalent of Pearls of Power for spontaneous casters.
Edit:
In reading it again, I think you were correcting yourself and meant ioun stone originally. What I said pretty much still applies. A smart enemy might realize they can damage the enemies ability to fight by attacking the ioun stones surrounding them, rather than directly damaging the enemy.