# How much should this homebrew ioun stone cost?

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.

• @AnneAunyme Although I think it obvious from omission, but does such an ioun stone have any benefit to the owner when not fast-spinning? – royalmurder Dec 11 '17 at 16:58
• @royalmurder: not by itself. Like for the other ioun stones it is still an item you can cast silence or light on, so you may have a use for it. – Anne Aunyme Dec 12 '17 at 9:44

5,000 gp is approximately correct for an item that deals 1d4 damage each round.

The closest benchmark I can find is the Horned Helm (Magic Item Compendium, 8000 gp) which grants a secondary gore attack (-5 attack) dealing 1d8 plus half Strength modifier damage.

This ioun stone is essentially a weaker version of that item. It deals around half as much damage, doesn't let you pick between multiple targets, and hits adjacent allies (although allies will rarely be adjacent to this unless healing you, so it's not as strong a drawback as it may seem). On the upside, it's slotless. It uses the full base attack rather than -5, but since it uses mental ability scores it's weaker on a melee character, and a spellcaster is rarely in melee, so that aspect balances out.

So 5,000 gp is around the right price for this item. To prevent someone wearing multiple of these to become a human chainsaw, I suggest that such stones attempt to attack each other when many are worn at once.

• Good call on benchmarking it. I wouldn't have thought of comparing it to a bonus natural attack. – Ifusaso Dec 11 '17 at 15:34
• The differences between the horned helm and this are much more extreme than you let on. You can have multiple of these and they stack, but only one horned helm, so the slotless matters more than it otherwise might (most ioun stones don’t self-stack). You only get the “free” attack with a horned helm if you were full-attacking anyway, while this gets in a freebie every round no matter what. But on the other hand, the horned helm is a proper attack—it scales in all kinds of ways and can get all kinds of bonuses. This cannot get any bonuses at all, and the base damage is pitiful. – KRyan Dec 11 '17 at 15:36
• (Not saying that horned helm was a bad point of comparison—as @Ifusaso says, that’s quite clever and I wouldn’t have thought of it—but you should address the differences more.) – KRyan Dec 11 '17 at 15:37
• @royalmurder If I had a suggestion for that, it would be in my own answer. In reality, I think the entire concept is incredibly toxic and bad for the game, and so would simply recommend not having any such ioun stone at all. I may write such a suggestion up as an answer, perhaps, but I also may not. But ultimately, 5,000 gp is not enough to prevent game-breaking abuse of this ioun stone—and I do not mean game-breaking in the “overpowered” sense, but literally in the sense of breaking the assumptions of the game’s narrative. But at the same time, 5,000 gp for just one is a waste. – KRyan Dec 11 '17 at 17:01
• I also think this item should break after X number of attacks. – Tyler S. Loeper Dec 11 '17 at 19:22

Magic item crafting is (loosely) based off of a table available here.

Pertinent lines are:

Use-activated or continuous Spell level x caster level x 2,000 gp

Note: If a continuous item has an effect based on a spell with a duration measured in rounds, multiply the cost by 4. If the duration of the spell is 1 minute/level, multiply the cost by 2, and if the duration is 10 minutes/level, multiply the cost by 1.5. If the spell has a 24-hour duration or greater, divide the cost in half.

No space limitation: Multiply entire cost by 2

So we get (spell level times minimum caster level) x 2000 x duration modified x 2

Since no spell does 1d4 damage per round, we have to compare it to similar spells. Cantrips can deal 1d4 damage per round, but take up your Standard action so they are siginificantly weaker than one which is 'set and forget'. The spells I found most similar are Heat/Chill Metal and Summon Swarm, both 2nd level spells (3rd minimum CL).

Therefore, according to general guidance, your price would be:

2x3x2000x4(measured in rounds)x2 =

96,000g. Or 48,000 to craft.

Arguably, this could be accomplished by associating it with Magic Missile instead. The resultant cost for a 1st level spell would be:

2000x4x2=

16,000 or 8,000 to craft

• Would you, under the most favorable circumstances, buy this item at this price? – Anne Aunyme Dec 12 '17 at 14:25
• No, I just wanted to provide an alternate point of view based on the literature provided. The rules allow that the outcome might not make sense and is up to the GM. But I figured having a highball answer might help with perspective (and is technically correct if not logically). – Ifusaso Dec 12 '17 at 16:58
• Honestly when I dredged up the table, I had no idea it would be that high. I'd personally estimated 20kg thinking it would probably be a 1st level spell (of which the closest is probably Magic Missile which isn't as good of an approximation as Heat/Chill Metal) and forgetting just how fast it multiplies up. The largest cost, as you can see, is the 4x for taking a spell effect (d4 damage) and having the option of always doing it, when you want. Reducing it to rounds per day or some such helps it out a lot. – Ifusaso Dec 12 '17 at 17:01

This is almost exactly a continuous version of spiritual weapon.

It is slightly less good in that the damage is lower, but close enough to cost it out according to normal item rules: spell level x caster level x 2000. Spell level is 2, minimum caster level for that is 3, so total base cost is 12,000. No space limitation doubles the entire cost to 24,000 gold.

That seems about right. While the damage is trivial, any stackable, slotless, free attacks break the action economy right in half. We know this from 3.5, where it came up as Persistent Spell shenanigans instead (e.g. persistent Cloud of Knives).

Overall though, @KRyan's earlier comment is accurate:

I think the entire concept is incredibly toxic and bad for the game, and so would simply recommend not having any such ioun stone at all....ultimately, 5,000 gp is not enough to prevent game-breaking abuse of this ioun stone—and I do not mean game-breaking in the “overpowered” sense, but literally in the sense of breaking the assumptions of the game’s narrative.

...which applies near-equally at 24,000gp.

• Spiritual weapon is a lot different. It's got a range of 100ft+10ft/lv for one, the lack of which is rather a key constraint on this stone. It gets multiple attacks per round, hits incorporeal monsters, bypasses damage reduction, deals force damage, requires you to detect an enemy to affect it, etc. It also requires a move action per target, which the lack of is kinda the big problem with this ioun stone. The only similarity is that it deals damage over time, which is hardly a similarity at all-- a mundane club is more similar! – the dark wanderer Dec 11 '17 at 23:07
• I don't see how you could break the game with this item if priced at 5,000 gp. Can you cite a precise case for one of these game abuses? (eg how many stones for which level) – Anne Aunyme Dec 12 '17 at 9:55
• @AnneAunyme This will depend on the campaign, obviously, but I think—based on this monster chart and this wealth chart—, that the breakpoint seems to be a 4-member party at level 11 when investing all of the party's wealth in these ioun stones means, without the PCs having to do anything but surround the monster, on average rolls, CR-appropriate monsters die to their 64-stone assault alone. Of course, no party would do that, but a party totally could. ;-) – Hey I Can Chan Dec 12 '17 at 11:36
• @HeyICanChan: my quick calculations with a party of 4 at level 11. I assume they face a CR 11 monster, which should be an easy fight: 145hp, 25AC, I assume no DR or other defensive abilities. The bonus to attack of the stone will in a good configuration be something like 11+3=14. It means half the stones hit, for a total of 32d4 or 80hp on average. so not enough to kill the monster. It may be too much, I am not sure about how much the stuff is supposed to do in an encounter. – Anne Aunyme Dec 12 '17 at 13:08
• If the monster is CR 13 instead (a medium encounter), 7/20 of the stones hit, so the average damage is 7/20*64*2.5=56 against 180hp, for CR14 it is 48 against 200hp and for CR15 40 against 220 hp. As a comparison a typical damaging spell can easily do 1d6 per level, for a total of 44d6 (if all the character are casting) or 154 damages. It will probably be "save or half", so 77 damages in the worst case. – Anne Aunyme Dec 12 '17 at 13:17