Items that glow when certain conditions are met? How much should creation cost?

[eyebreaker7]

How much should it cost to make an item (usually a weapon) glow when certain conditions are met? Like Sting from LoTR or like the Frostbrand with temperature or a Helm of Brilliance and undead? I thought it was an ability that when with a bane weapon but I don't see it spoken of anywhere.

[GrayDeath]

That depends incredibly on the usefulness of the effect, the range of the effect, and the world/Setting.

Throwing a few numbers into the room:

From 1 Gold Coin (Door Grip glowing red if someone behind the door is on the toilet^^) to 50000+ Gold (Sword/etc glowing in a specific color if a specific kind of high level, well cloaked, Demon/Devil/Whatever is in your range), I`d say.

Ergo usefulness, Range, what the Item needs to pierce/overcome to actually detect what it is meant to detect, and so on.

[InvisibleBison]

I'd say glowing when creatures of a given type or subtype are nearby - that is, within a few hundred feet - is roughly as powerful as a first level spell. So allowing a weapon to do it would cost 3,000 or 4,000 gold, depending on whether you think detect animals and plants (http://www.d20srd.org/srd/spells/detectAnimalsOrPlants.htm) or detect undead (http://www.d20srd.org/srd/spells/detectUndead.htm) is a more reasonable basis for this hypothetical detection spell. I'd say that it would be roughly a +1 bonus, and maybe make the bane property do it as well for free.

[Thurbane]

Eye of the Druuthbane (Magic of Faerun, p.157) is a crystal that glows when doppelgangers and/or illithids are within 60 feet. It also provides +4 to Will saves, and fires a ray that can force doppelgangers into their true form 1/day. Priced at 18,000gp.

[Doctor Despair]

Sense Heretic kinda does this as a level 1 spell (Paladins only, but Archivists could cast this from level 1). It lasts 10 minutes/level. Making it a wondrous continuous effect technically would cost 2000g. Embed it in a weapon like a jeweled hilt and get a DIY Sting, but for evil divine casters. Probably a little cheap for this kind of detection, to be honest, but the precedence is there for it.

I'd think trading out alignment/casting for a subtype would be balanced if you're creating a custom item. Glow for vermin!

[Dimers]

I'd make it free, just a 'ribbon' or flavor ability. It's as likely to cause problems ("Oh, were you trying to be stealthy? So sorry ...") as it is to reveal important information to the players in a way they can use.

[sleepyphoenixx]

How much should it cost to make an item (usually a weapon) glow when certain conditions are met? Like Sting from LoTR or like the Frostbrand with temperature or a Helm of Brilliance and undead? I thought it was an ability that when with a bane weapon but I don't see it spoken of anywhere.

Fiercebane (MIC) is a +1 enhancement that requires Bane and makes your weapon glow when a creature of the relevant type is within 60ft.

[Thurbane]

Fiercebane (MIC) is a +1 enhancement that requires Bane and makes your weapon glow when a creature of the relevant type is within 60ft.

Never noticed that before. Perfect answer to the question. Also does extra damage on a crit to the creature type.

[nijineko]

fiercebane is the classical LotR option.

A percentage of magic weapons either glow constantly or glow on command, it's in the DMG.

Making any item glow under circumstances is pretty easy, actually simply use the light spell and the detect spell as prereqs for item creation and presto, you have a sword which glows whenever it detects whatever the crafter set it to. Fairly cheap too, and as a tiny bonus over fiercebane, not limited to creatures. It can detect anything that a detect spell can. also, interestingly, the magic mouth spell has guidance on how detection works.

[Thunder999]

Well weapons can glow for free and light is a cantrip so the actual glow is worth at most 500gp for a use activated cantrip and might be free, or perhaps we go 50gp because that's the value of a continual flame.

Then it's just the price of however you do the detection, which could be a locate creature spell or perhaps something like detect evil or detect magic, the latter two could reasonably even be set to glow only for auras of sufficient strength.

[Vaern]

A certain percentage of all magic weapons glow by RAW without affecting price.
There's also a list of conditions for intermittently functioning items. You could theoretically apply this aspect to a single ability on the item (the light) to make it only function in the vicinity of a specific type of creature (orcs) and adjust the cost of that single ability accordingly (-30% of free to make the ability free, for example).

[PraxisVetli]

Eye of the Druuthbane (Magic of Faerun, p.157) is a crystal that glows when doppelgangers and/or illithids are within 60 feet. It also provides +4 to Will saves, and fires a ray that can force doppelgangers into their true form 1/day. Priced at 18,000gp.
That's such a niche item. Almost useless, untill you need it and it's awesome. How long is the dopple stuck; can it just immediately reshape on its turn?

[Thurbane]

That's such a niche item. Almost useless, untill you need it and it's awesome. How long is the dopple stuck; can it just immediately reshape on its turn?

Yeah, I wouldn't even have known it existed, but I stumbled on it while I was looking to contribute to this thread: Mind Flayers, Beholders, and Aboleths Oh My (https://forums.giantitp.com/showthread.php?616594)

Looks like the duration of being forced into it's true form is 1d4+1 rounds.