Magic Item Crafting: Wondrous item that "reacts" to an attack with a spell

[Zin Z'arin]

I have a player who is getting very involved and creative with crafting (both mundane and magical). He has a new idea for an item (a brooch or bracers, probably) that casts a spell targeting his attacker in response to an attack.

I'm trying to be very cautious with this one, as it has high potential to unbalance the game; it effectively allows the casting of 2 standard action spells in a round (his normal standard action and the spell from the item). Even mythic tier abilities that grant additional actions in a round specifically prohibit using the extra action to cast a 2nd spell.

His vision right now is an item that, x times per day, would respond to a melee attack with a hold person/hold monster spell on the attacker. He has also mentioned blink on himself as an alternative. If I move forward and allow him the item, I could also see this go another way, wherein it is a spell vessel that could be charged by him with any spell of his choice, that would then go off on the next melee attacker.

Does anyone have any advice? Are there existing magic items that do anything similar?

[Dracoknight]

There is already something like that: "Spell storing" on armor.
When a attacker hits you can as a free action that spell will be unleashed apon his face, similar to spellstoring in a weapon.

But it will target the attacker, so if you want a defensive spell cast on yourself you could have a similiar setup, plus the spell storing is one-shot but you can refill it with your own spells or scrolls.

[Cussune]

There's the Spell Storing armor enchantment, it's +1.

*EDIT* I found my first ninja!

[Zin Z'arin]

Perfect; thanks! I should have seen that, actually. :) That will be a great way to model this effect (and it gives me confidence that I can do it in a way that maintains balance).

[skizzerz]

Dracoknight wrote:

There is already something like that: "Spell storing" on armor.

When a attacker hits you can as a free action that spell will be unleashed apon his face, similar to spellstoring in a weapon.

But it will target the attacker, so if you want a defensive spell cast on yourself you could have a similiar setup, plus the spell storing is one-shot but you can refill it with your own spells or scrolls.

Spell storing armor is an immediate action, not a free action (spell storing weapons are free actions, so I think that's where you got confused).

[Dracoknight]

skizzerz wrote:

Spell storing armor is an immediate action, not a free action (spell storing weapons are free actions, so I think that's where you got confused).

Yup, i mixed up my terms there.

Cussune wrote:

*EDIT* I found my first ninja!

*shhhh* they will hear you...