Improvised Magic Investigation Rules -- what would you have done?

[Ionathus]

Last night, one of my players used Detect Magic to inspect a plot-critical amulet (a suspicious NPC had been wearing it and claimed it had been mind-controlling them, but the PCs didn't 100% trust that and wanted to corroborate).

Because this is a high-powered magic item created by a very powerful being in a circumstance where they'd be expecting PC scrutiny, I had decided ahead of time that this amulet contained safeguards like Nystul's Magic Aura and similar defenses against "I cast Detect Magic / Identify and learn everything immediately."

I'd wanted identifying the amulet to be challenging but solvable by the players once they had obtained it, but in classic PC fashion they did something clever and got their hands on it way earlier than I was expecting (thus, I hadn't devised the mechanics of the challenge yet). So last night, I had to improvise that "diagnostic challenge" on the spot. I'm pretty happy with what I came up with, but am curious what your thoughts are and what you might have done in my position.

Spoiler: The improvised homebrew:

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When my party's Necromancer wizard tried to investigate the amulet's properties in detail, I asked her "what school of magic would you like to rule out?" She suspected that the amulet had Abjuration, Illusion, and especially Enchantment properties, but she said "Necromancy" to establish a baseline/control group using her field of study -- which I thought was a really fun and analytical approach!

I then asked her what her highest-level Necromancy spell prepared was -- 7th level, and I said great, roll 7d8, your DC is 20. She passed it easily, and she determined conclusively that there was no Necromancy on the necklace. The party was excited but some of them probably saw what was coming next...because this wizard PC is morally opposed to almost all Enchantment magic (messing with free will is a massive taboo for her) and thus, she does not have a single Enchantment spell prepared. 3d8 was the minimum roll if you didn't have the school prepared at all, though of course that only gives a ~6.5% chance of success -- fittingly, about the odds of a nat 20!

She whiffed on the Enchantment check and was gearing up to try on Abjuration next when she got interrupted by the consequences of the party's actions, and we wrapped for the night shortly afterward, with her planning to try Abjuration next.

Spoiler: Afterthoughts

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I'm pretty satisfied with it overall! My favorite part was introducing a challenge that's mostly in the party's favor, since they're high level (14), but it still plays into this specific PC's chosen strengths and weaknesses -- she's strong in Necromancy but shuns Enchantment almost entirely, so her lack of knowledge has minor consequences. This is especially exciting since this wizard PC has repeatedly ranted that all the schools of magic are useful and over-investing in a single area weakens you as a magic user -- and now she's facing the (again, minor) consequences of disdaining Enchantment!

I liked this homebrew, and I'll probably be tweaking it and using it for identifying/dispelling high-powered magic items or effects in the future. I won't add it as a blanket homebrew to Detect Magic or Dispel Magic, though: I don't like the completely binary "it either works perfectly or fails completely" mechanic but I understand why it exists and want to honor the intention. Those spells are a resource expense, and I certainly don't want to take the players' toys away from them. I stand by having them work by RAW 99% of the time.

However, when the question of "what is this weird magic thing" is the central focus of a challenge, I like having something like this in my back pocket that adds more weight to player choice and the roll of the dice.

Revised version of the homebrew:
When you use a spell to attempt to identify or dispel a very powerful magical item or effect, especially if its creator has protected it from interference, you may need to draw on your own practical knowledge of magic to accomplish your goals.

Declare a school of magic that you want to either identify or dispel on your target. Instead of rolling a d20 and adding modifiers, you will roll a number of d6s equal to your highest-level prepared spell of that school (minimum 3d6) and compare the total against the target's identification/dispelling DC, which is the same across all schools of magic for this target.

Spellcasters with spellbooks may use any spell written in their spellbook for this calculation, regardless of whether they have it prepared or not.

On a successful check, you identify or dispel all effects of that school of magic on the target. On a failed check, you learn nothing and may suffer additional consequences determined by the creator of the magical effect or item: the target may damage you, release a booby-trapped spell, expend one of your spell slots, force you to make a saving throw, or inflict some other effect at the DM's discretion.

You may attempt to identify or dispel multiple schools of magic on the same target as part of the same casting of your triggering spell (Detect Magic, Dispel Magic, etc.). In most cases, each school of magic takes 1 round to identify or dispel, and consumes your action for that round. If you wish to repeat the process on a school of magic for which you have already failed, you will need to cast the triggering spell again.

Spoiler: Revision thoughts

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I tweaked a few of the numbers to make it useful for all levels of spellcaster, though I don't love my numbers here -- they're usable, but probably could use polishing. Also, I think it's probably more fair to have a Wizard PC roll using the highest-level spell in their spellbook, rather than prepared spells, though this is only a meaningful distinction for a Wizard (Divine casters technically have all the options available, etc.). I like it for giving the Wizard's spellbook choices a bit of extra value -- having your education help you out passively feels like a very Wizard thing.

Overall I'm pretty happy with this as a "big magic" challenge, especially when the PCs get powerful enough to be slinging around lots of spell levels and encountering enemies who would logically have the resources to do something fancier than just "Nystul's Magic Aura." Best used in extreme moderation, but for those times when it's relevant, I like it.

What are your thoughts? What would you tweak? Or would you go off in a totally different direction?

[NichG]

I guess I'd go in a different direction if I had time to prepare and anticipate and add to a larger homebrew document, but maybe not if I was caught on the spot like you were.

Like, it sort of bothers me that in D&D most of the ways of interacting with magic have to do with binary spells that do or don't do a thing, when there's a skill system and when at least one magic set of spellcaster archetypes are high Int, and therefore high skill. So what I'd want to do is establish systematically across a number of different cases that the expected flow of investigating something where magic is involved passes through skills like Spellcraft and Knowledge(Arcana) and UMD and even Appraise. I'd want to shift a bunch of the diagnostic spells to be more about in some sense 'giving you things to use those skills on' that you wouldn't have otherwise or modifying those skill checks, than directly providing information.

But it means establishing those things before people pick their builds...

So e.g. the broad system (3.5ed taken as a base) would be:

- Spells are a transient Pattern of Energy in a Place - those three capitalized terms are each variables that a spellcaster can tweak to make a spell easier or harder to identify or detect, and to alter the details of a spell's effects. The Pattern contains the detailed information about 'what the spell actually does', the Energy flowing through the Pattern is what enables the spell to do it - this is the thing that ends up being [Fire] or [Positive] or [Vile] or whatever - and the Place is the layer of reality being used to carry the pattern and to transmit the spell to its target - usually this is the Material Plane but there are tricks which can place it in the Astral or Ethereal; Conjuration as a school involves making Patterns that displace themselves to other planes, so Conjuration spells more often leave signatures in different Places or are entirely located in a different Place. The Pattern and Energy of Illusion spells generally exists primarily in the Plane of Shadow and touches on the material only where the illusion manifests.

- Anyone who can cast a spell can at some level 'form Pattern' and 'feed Energy' without needing specific spells to do it. Essentially, you can sacrifice a spell slot and take the energy associated with that spell slot and 'poke' at anything magical in an attempt to modify it, dispel it, figure out what it is, etc. This is a UMD check, based on exactly how complex a thing you're trying to achieve. Generally speaking it only costs a cantrip slot to emulate a kind of low level 'magic touch' where you can get a feeling of ambient magical energies, like a poor emulation of Detect Magic. Actually disrupting a spell (improvised Dispel) requires a slot equal to that of the spell you're mucking with. You can take a very large penalty to overcome this gap with skill (-10 penalty per spell level of difference), but you don't get a bonus for overcharging. Sorcerers and spontaneous casters use these same 'mental muscles' when they cast, so they get a bonus equal to half their caster level when interacting with magic this way; other casters can still do it because fundamentally they have to be able to touch magic to cast magic, but the kind of formal structures around their casting style mean that they don't get practice in feeling out nuances of magical effects by hand as part of advancing their class (of course they can still invest in UMD).

You can also try these things just using 'pure UMD' but it's at a 10 point worse penalty compared with using a cantrip slot.

- Enchanted items are like Spells except they also have an Anchor which binds the magical pattern to the item, and a Fountain which acts to gather energy from the universe in order to continually power the spell. The Anchor is something which has to be physically part of the item, though it can be hidden - hiding the Anchor is a function of a Craft check made while enchanting the item, while finding it is a Search check. The Anchor gives you enough information to know that the item is (or at least once was) enchanted, as well as the Place the enchantment's Pattern lives (with a Knowledge(Planes) check). The Fountain is generally constructed from the material components needed to enact the enchantment, and must be connected to the Anchor and physically on the item - if you can identify the Fountain, it tells you the type of Energy the spell uses (with a Knowledge(Arcana) check), but Fountains can be made of things used as decoration and do not automatically reveal the presence of unusual magical energy - in this setting, a high quality ruby has a background Fire elemental magical charge whether or not it's used as part of an enchantment.

- Artifacts are special in that they're metaphysically extended objects that exist across planes. This allows their Anchor and Fountain to not actually be on the object itself, and contributes to their relative indestructibility. Whereas a standard enchanted item gathers magical energies from its environment with a collector on the object, an Artifact is like a kind of realer-than-real illusion which is being continuously created by a locus somewhere out on the planes, often tied with an entire divine realm. That locus beams structured power across the planes to wherever the Artifact's physical avatar may happen to be - if it loses a lock on a specific physical avatar of that power, it might even convert some similar object elsewhere into the Artifact spontaneously. Disjunction sends a backlash along this connection, giving it a chance of damaging the source locus of the Artifact's power, but also risks the residual connecting function of that source locus overloading the caster with now-malformed power, basically 'jamming' their ability to directly shape magic themselves.

- Relics are a special case of conditional artifact where some powerful being uses a physical object as a beacon, but then directly provides their power to the wielder of the object as an act of will. Basically the only thing innately magical about the relic is that in some way it's visible to the right kinds of senses from other planes. If you can figure out what those particular senses are, you can use that to detect a Relic, but standard stuff like Identify and Analyze Dweomer won't be great for this. Legend Lore on the other hand would give you a big leg up here.

- Naturally magical objects are often just highly concentrated Energy with very little shaping to them. It isn't that hard to identify the associated Energy even without magical assistance, because it will often have distinctive visual and tactile cues - Fire feels unnaturally warm, Negative energy gives feelings of weakness and unease, etc. Fairly low Knowledge(Planes) check to get this stuff. Sometimes there's a bit of Pattern associated with biological natural magic (e.g. body parts of fantastic creatures) but this is extremely hard to get out - you'd essentially need magic capable of genetic engineering, which is generally epic spell territory. Still, wouldn't be impossible for a specialized 6th level spell.

- Natural magical fields have Patterns that exist in their environment, often at massive scale. Things like the feng shui of a valley can act as a natural Pattern that creates a localized magical effect somewhere within that valley given the availability of the right elemental energies. The Energy of a natural magical field is the most accessible indicator, and its Place is almost always the same plane that the field is on. To determine the Pattern (and therefore what the field does from first principles) you'd need e.g. a geological survey or other information putting together a map of the area, the ores in the soil, etc - whatever thing has naturally self-organized into defining this magical effect, different for each case. Learning that Pattern might let you craft a spell that replicates the effect of the natural magic.

- Aside from all of this, you can skip the ivory tower theory of 'why does a spell do what it does?' and directly investigate the *effects* of a spell. For example, with a Knowledge appropriate to a creature - generally Nature, but swap in Religion for undead etc - you can identify whether its stats have been modified, whether its under mind control, etc. This evidence is enough to draw conclusions about the school or even the specific spell in play, though converting 'I think this creature is under magical mind control' to 'I think this is specifically a CL 13 Dominate Person' also requires a Knowledge(Arcana) check. Knowledge(Planes) here acts as a stand-in for what should be a Knowledge(Metaphysics) or the like (which I'd be tempted to just have separately) in identifying conceptually weird effects - 'this field forces you to act according to the abilities of an alternate reality version of yourself', 'this field turns colors into emotions', etc.

So there are various ways to figure out what a spell or magical field or enchantment is and where it is and how to interact with it:
- Seeing somatic components or hearing verbal components lets someone deduce the Pattern with a high enough Spellcraft check. You don't need Detect Magic or Arcane Sight or anything for this.
- Seeing any visual manifestations of a spell lets someone deduce the Pattern and the Energy, but the check is harder.
- Detect Magic and Arcane Sight allow you to see the Energy of a Spell that is in the Material plane (or the same plane you're on), which in turn lets you directly inspect its Pattern.
- The Identify spell injects a trace into an object's Fountain, returning the Pattern to the caster once the magic item has used that energy. At the level of Identify, the item's magic needs to be engaged to get the full pattern. For an item waiting for a command-word for example, Identify would first reveal the Pattern associated with 'listen for this command word' (where the specific command word could be figured out with Knowledge(Arcana) from seeing the Pattern), but it wouldn't automatically reveal the Pattern of what happens when you use it. Cursed items use this limit to hide their effects by being highly conditional - if you don't actually hit it with Identify when its doing the bad thing, you might instead see the always-on Pattern the crafter wanted you to see.
- Analyze Dweomer is more aggressive and reveals all Patterns associated with a magic item (though it in itself does not decode them). Obfuscation of Pattern is the best way to hide from this, or have the item be a Relic and just be mundane until the specific moment it isn't.
- Nystul's Magic Aura displaces the Energy and Pattern of a Spell to the Plane of Shadows. Not impossible to defeat, but mostly blocks casual discovery.
- Things which impact the connection between where you are and the Place where a spell is can block that spell from functioning. This is the principle behind selective anti-magics like Globe of Invulnerability, Spell Immunity, as well as certain kinds of Dispelling. Some of those spells need to be modified to be more specific about this.
- There are new spell variants that specifically let you look into the Ethereal, Astral, and Shadow planes to see if casters are hiding their spell there.
- There are new low level spells that let you 'light touch' those planes in order to manipulate or place magical patterns there.
- Certain existing metamagic feats are now interpreted as letting you shift the Place of a spell intentionally in order to conceal it or avoid bad interactions. This can also be improvised on the fly with an epic Spellcraft check, but failure means losing the slot or even a wild surge.
- Successfully analyzing the Pattern of a spell also lets very skilled characters identify its variable parameters. E.g. you can not only tell 'there's an Illusion spell here' or 'its Disguise Self', but specifically 'this Disguise Self changes the ears, eyes, and haircolor in such and such a way'. Basically, beat the DC by 10 and you get more detail. If you beat the DC by 20, you can know things about the caster as if you were doing handwriting analysis - where they learned the spell (what major cultures used this pattern vs another variant?), what sort of caster, what caster level (how perfect are the lines?), even their race and height and weight and so on. If you beat it by 30 you can get the answer to specific questions about the circumstances of casting - was this their last spell slot or were they full up, was it made at day or night time, full moon or new, etc?

You can obfuscate Pattern in various ways with Spellcraft:
- You can use a non-standard Pattern or introduce extra unnecessary elaborations in the Pattern of your spells or enchantments. This is a Spellcraft check - for prepared casters, made when they memorize the spell; for spontaneous, made at casting; for enchanting, made when the enchanted item is crafted. If this is higher than the basic DC to identify the spell effect, it replaces that DC.
- You can piggyback on a closely related spell. Usually this is limited to something where a choice made at casting can go in different directions - you use the same framework, but you make multiple choices and only 'hook one of them up' to the actual energy flow. Like the above case, but limited in that your piggyback spell has to be sufficiently similar to do this at all, but what you gain is that when someone hits the basic DC but misses your DC, they think the spell is the one you piggybacked on rather than the true spell. Usually not worth it, but for espionage or curses its kind of core - hide an alternate identity under a commonly used cosmetic spell, etc.

So anyhow, I'd try to pepper that kind of thing throughout the system and keep it in mind. So like, when someone says 'this is Evocation' its not because it had the evocation glow (in this version) but rather because there's a bunch of evidence that is consistent with how Evocations tend to work - its Place is primarily the Material, it has a strong single-typed Energy signature, the Pattern is simple and has parts of it which convert raw magical energy into the target type, etc.

Similarly, if someone was trying to figure out a new spell effect from the Pattern, having this kind of language would allow more detailed partial success - 'well you can tell from the Pattern that this spell draws from the Astral somehow, but then it does this complicated thing you can't figure out; however, the targeting seems to have a kind of latch-like mechanism where the effect binds to the first person to put the item on, and then continues to feed this to them even when they remove the item; also there's stuff in there that reminds you of the kind of thing you have to do to get magic to interact with thought directly.'

[Vogie]

This is one of the problems with how the system kind of quashes certain types of storylines.

Everyone in McGuffin town is being effected by a terrible curse! Can you find out why?

Nope, that seems hard. Instead, we're just going to go collect a bunch of paladins, clerics, warlocks and wizards from the surrounding cities and towns, have them prepare Remove Curse, and work our way through everyone. It'll take a couple days, but it'll be fine. We can solve this problem in downtime!

One of the ways that you can use to get around these things is by having the "cure" or "reveal" options uncover a new quest. When the party uses things like detect magic or identify, you find out morsels of information that will lead them to the truth, rather than just exposit the information immediately.

Spoilers from a movie that came out a half-decade before my birth:

Think of how, in Indiana Jones and the Raiders of the Lost Ark, it treats the plot-jumpstart artifact, the Headpiece to the Staff of Ra. All they know ahead of time is kinda what it looks like - it's round, there's a bird with a gem - but once it's identified, it doesn't just say "you'll never guess where we're putting the Ark - it's over here!". No, it just says the the staff for this should be X length. The heroes have to still get the object, make the staff the right height, travel to the dig site, sneak into the map room to find the real location, and then go to the new indicated place, just to get into the dungeon where the titular artifact is hidden.

Whenever you have a plot-critical magic item, you'll want to do something like that. When they detect magic, they realize it's shrouded - when they identify it, they get a riddle, prophecy or set of directions. You want it to be relatively straightforward - nothing like the super-vague "I open at the close" phrase from the Harry Potter series, more like "Sanctum of the Sun, Whole of the Moon". Something that can be figured out or pieced together pretty quickly, just have to figure out where the nearest alter to the sun is and when the next full moon is.

If you want more crunchy reasons why these things happen, you could include:

• Multiple Pieces, scattered about. Until it's complete, the pieces only point to each other. Once it's complete, only then can you read/identify the whole thing.
• Ancient magics. Just like we've been attempting to remake Roman concrete unsuccessfully for hundreds of years even when we've had the recipe - because when it says "water", we assumed freshwater (because that's how we make concrete now), but they used saltwater (because of course they did, it was in the single and double digits years CE and freshwater was much more rare). The ancient artifact could require the presence of blood, specific times of year, or be in the presence of a leyline before it shares a secret.
• Ancient or foreign languages. The spells of identification see into what is hidden, but what is revealed doesn't make any sense. This type of things was made famous by the Tamarian language from Star Trek, in which the aliens speak entirely in metaphor and their own literary references. In that setup, "a gift" would be communicated as "Temba, his arms wide"; an English equivalent given is something like "I miss my significant other" being communicated as "Juliet, on her balcony, lamenting" - a perfectly understandable phrase, that also is complete nonsense, if you don't understand the reference to the Shakespeare play. So the party "identifies" the object, and now has to figure out what that means - likely hunting down an elderly native speaker, or cloistered scholar/researcher, who will inevitably want something from the party before/while they are translating the information.

[brian 333]

I once played a 1st Ed Ranger/Magic Tracker. I had to take Magic User as favored enemy, but the system we worked out was not dissimilar to yours.

Length of time a magical aura lingered, residual effects to determine school and specific spell, and caster 'signature' were all details we worked on during several months of play.

But you did well on the fly, especially revealing things in layers. "What, specifically, is your character doing? Now roll for that!" It is a much better way to handle what should be a solvable mystery than an infodump.