Houserule for recognizing spells with Arcana

[Iguanodon]

Some DMs apparently allow players to try to recognize spells with Arcana checks, even though that's not what the Arcana skill is even used for. This is my attempt to come up with rules for when characters can and can't recognize magical effects. I tried to cover all the bases; let me know if I missed anything important.


Any character may infer that a spell is being cast when they hear incantations, see gesticulation, or notice the use of material components or a spellcasting focus.

When a spellcaster is attempting to conceal the casting of a spell with material or somatic components, they must succeed on a Dexterity (Sleight of Hand) check against the Passive Perception of any bystanders. To conceal verbal components, the caster must be more than 15 feet from any listeners, or, if something loud is distracting the listeners, they must succeed on a Wisdom (Stealth) check against the listeners’ Passive Perceptions. A spellcaster may not successfully conceal their spells’ components when someone is carefully observing them from nearby.

The Subtle Spell metamagic completely conceals the casting of a spell from all observers.

Proficiency in the Arcana skill denotes a certain amount of knowledge of the arcane arts. As such, characters proficient in Arcana may attempt to more specifically identify spells as they are cast. This is not a replacement for the Detect Magic spell.

When a character proficient in Arcana notices a spell being cast, they may attempt to recognize it based purely on the style with which it is cast. They make an Intelligence (Arcana) against the caster’s spell save DC. On a success, they correctly identify the school of magic the spell belongs to. On a failure, they do not recognize the spell. They may still recognize its effects if they are personally familiar with the spell in question. Wizards belonging to the school of the spell recognize its school immediately without a check.

Monk subclass effects that replicate spells are not actually spells and are not subject to these rules.

Thoughts? I'm wondering if using the spell save DC is good enough or if the spell level should play into how hard it is to recognize.

[JumboWheat01]

The thing about somatics is that it isn't just finger waggling. For example, Burning Hands describes the spell as putting the thumbs of your hands together and spreading your fingers, a rather obvious position, especially to another wizard. Then there are quite possibly spells that require rather dramatic or violent arm movement.

I know it's perfectly possible to "fail a spot check" in a d20 game, but sometimes the obvious is just a little too obvious to hide. In order to hide your somatic parts of the spell, you'd have to change your whole somatic movement, and that could quite possible hinder your spell and cause it to fizzle since it's not how you learned to cast the spell. It's like trying to cast in armor you aren't proficient with, the movement distractions prevent the spell casting.

Hiding the Verbal though, I'm totally with that. There's nothing that say you have to use your OUTDOOR VOICE in order to cast a spell, at least not that I remember it. It's more about tone, not volume. You could totally whisper your spell's verbal component and get away with it in my books.

As for Material, well, a spell casting focus can easily hide the normal stuff, and unless the spell says you need to present the material in a very obvious matter, it should be pretty easy to hide with a slight of hand check.

As for using Arcana to recognize the spell school while it's being cast, I like that. Neverwinter Nights 2 had a few different auras that popped up based on school being cast, like Illusion, so I can see something like that working. Plus, if it IS an Illusion being cast, you could totally use a HELP action to get your party members to realize that it is in fact an Illusion and shouldn't be trusted.

[Iguanodon]

I'm sort of thinking that spells with very specific somatic/verbal/etc. components (like Burning Hands or Command) might override this rule I made based on the general 5e logic that in cases of rules conflict, specific beats general. This is outlined in the PHB somewhere; I would cite it but sadly I don't have one with me right now.

Anyway, I hadn't thought about any external factors like armor penalties, etc. I think any issues with casting in armor would be rolled into proficiency (which is why wizards don't get armor proficiency at first) rather than doubling up on penalties.

[Tanarii]

How are they recognizing it? Nothing says that V and S components aren't unique to a given caster for a given spell. In fact, they may not be the same every time a given caster casts the same given spell, he may have to use them differently each time to designate targets, range, angle of area of effect, etc. Furthermore S components in conjunction with M components almost have to be different when cast with a focus instead of a M component.

Edit: Short version ... I don't allow Arcana to be used to recognize spells being cast.

[Iguanodon]

How are they recognizing it? Nothing says that V and S components aren't unique to a given caster for a given spell. In fact, they may not be the same every time a given caster casts the same given spell, he may have to use them differently each time to designate targets, range, angle of area of effect, etc. Furthermore S components in conjunction with M components almost have to be different when cast with a focus instead of a M component.

The inspiration for this idea was that each school of magic has its own "style" of casting spells, and the general style of gesticulation and speech would be recognized, not the spell itself.

Are there any cases where this reasoning doesn't make sense? I know it would be very setting-dependent of course, since the internal rules of magic vary between settings.

[Tanarii]

Are there any cases where this reasoning doesn't make sense?It makes sense if the DM is defining how casting works, instead of the players. Or if they're a non-rotating group that can work together to decide that's the way spellcasting works within the campaign. But if each player is deciding how they cast spells and what V & S components mean for them, within the rules, then it wouldn't work.

[Slipperychicken]

The inspiration for this idea was that each school of magic has its own "style" of casting spells, and the general style of gesticulation and speech would be recognized, not the spell itself.

Are there any cases where this reasoning doesn't make sense? I know it would be very setting-dependent of course, since the internal rules of magic vary between settings.

I'd justify it like this. Somatic and verbal components are not unique to spells, but their combinations tend to follow subtle patterns which can be recognized with training and experience, and also inferred from context. The variable nature of spell-gestures and vocalizations is exactly why a roll is required in the first place. To a seasoned observer, recognizing a spell is like guessing the content of a sentence from the first few words, or recognizing tune from just the first notes.

[Tanarii]

Somatic and verbal components are not unique to spells, but their combinations tend to follow subtle patterns which can be recognized with training and experience, and also inferred from context. What if the components are unique to the caster? In other words, he invented them himself, and the underlying pattern is unique to that caster?

It might be possible to figure it out anyway, assuming they share some common culture. But even then, it'd be like trying to decrypt a substitution cipher using wing dings when you've never heard of them and you don't speak the underlying language. In six seconds. Unlikely.

Obviously this is all campaign specific. I'm just presenting other ideas of how casting might work in ways that make this impossible. Given that it's more or less the current rules that you can't do it. If you (or the OP) *want* it to be possible, your idea is a great justification.

[MaxWilson]

What if the components are unique to the caster? In other words, he invented them himself, and the underlying pattern is unique to that caster?


"Forzare!" Wham.

"Fuego!" Whoosh.

[Pex]

Since Sorcerers get Subtle Spell those who know would recognize what's going on. It is fair to say only those proficient in the skill can attempt the roll.

It adds complexity, but one idea is for the DM to always also roll a d20 behind the screen. In many situations it doesn't mean anything. However, if the PC rolling is a wizard and the NPC is casting a spell of his specialization, the DM's roll is to give the player Advantage. If the PC is a cleric and the NPC is casting a bard spell and also of a higher level than the cleric could cast, the DM's roll is to give the player Disadvantage. If the PC is a sorcerer and the NPC is a wizard casting a spell the PC doesn't have but is of a level he could cast, the DM's roll means nothing and just the player's roll counts, the default setting. This way the DM doesn't have to tell the player to roll with Advantage/Disadvantage and inadvertently give the player some metagame knowledge.

[Iguanodon]

Alright, there are different interpretations of how casters cast spells, I get it. But assuming it is possible to identify spells in the first place, what do you all think about the balance of this system?

Right now, I'm restricting this ability to characters proficient in Arcana rather than spellcasters in general, so a sorcerer or cleric or paladin who isn't proficient in Arcana wouldn't be able to do this. Is this okay, or should I not be relying on "proficiency" so much? What about expertise? Should Jack-of-all-Trades (bard ability, 1/2 proficiency to all skills) count?

Also, I mention some specific DCs (passive perception, spellsave). I think it makes sense that the difficulty of recognizing a spell might vary depending on how advanced the techniques are rather than how skilled the caster is, but it's hard to say. Any alternatives to using the spell save DC?

[JoeJ]

Alright, there are different interpretations of how casters cast spells, I get it. But assuming it is possible to identify spells in the first place, what do you all think about the balance of this system?

In terms of balance, being able to identify spells is a buff to Abjurers and a nerf to Illusionists. In general, that's probably good for combat-as-sport, because Counterspell can be used more intelligently, and bad for combat-as-war, because it makes creative use of illusions harder.


Right now, I'm restricting this ability to characters proficient in Arcana rather than spellcasters in general, so a sorcerer or cleric or paladin who isn't proficient in Arcana wouldn't be able to do this. Is this okay, or should I not be relying on "proficiency" so much? What about expertise? Should Jack-of-all-Trades (bard ability, 1/2 proficiency to all skills) count?

That's a departure from the way skills are handled in 5e. Everybody can make skill checks for anything that skills are used for. Proficiency just lets you be better at something.

[JackPhoenix]

In terms of balance, being able to identify spells is a buff to Abjurers and a nerf to Illusionists. In general, that's probably good for combat-as-sport, because Counterspell can be used more intelligently, and bad for combat-as-war, because it makes creative use of illusions harder.

The second problem is mostly solved by requiring proficiency in Arcana. Most enemies aren't proficient, so they still can't recognise illusions from anything else


That's a departure from the way skills are handled in 5e. Everybody can make skill checks for anything that skills are used for. Proficiency just lets you be better at something.

It is a departure, but something I do myself (inspired by 3.5 "trained only" skills). In some cases, you need to be proficient in a skill to even get a roll (nope, you can't perform successful brain surgery just because you're lucky). In other cases, if you're proficient in the skill, you autosucceed, while someone non-proficient still gets to roll (if it's something a professional can do routinely and it's not impossible for amateur to do...mostly with "lore" skills). It worked pretty well so far.

[Sitri]

By reading the "spellbook and copying spells" sections, I get the impression that spells (at least for a wizard but you could extend rationalizations to others) are like writing programs. Not all programmers are going to do it the same way, they have their own boiler plate, methods, system checks, routing, and/or sloppiness that is their own. However, a programmer looking at another's code can figure out what the other is doing with varying degrees of effort. So even if a caster would do something different himself, he may recognize some bits of code and realize what the other person was getting at.

I am about to start of a game and would like to incorporate something like this; all the players have more of a history with 3.p where this was a standard use of Arcana.

My main concern is one mentioned above: I don't want to gimp illusion spells. I thought about saying the DC to recognize an illusion is built in from the start of casting before you get a chance to identify them, but that still gives a free check in many cases. I considered saying you still need to disbelieve the illusion by conventional means even if you identified it during casting, but this feels rather clunky to me.

[Sredni Vashtar]

How about giving Illusionists and illusions a bonus or advantage to not being detected?

[georgie_leech]

In keeping with the theme, a check against Illusion spells failing by a certain amount could give you the wrong information. As in, you identify it as a different spell entirely, not just 'you don't know what spell it is.' This works better if the Arcana check is made by the DM secretly, of course. As a player, I'd be rightfully suspicious if I rolled a 2 and the response was 'you recognise the spell as a high level Conjure Celestial,' or whatever. Note that this means that all of the checks would have to be made by the DM in this case, otherwise the DM making the check might as well be a sign saying 'ILLUSION SPELL BEING CAST' which kind of defeats the purpose.

[Iguanodon]

Illusion spells is something I hadn't thought about, and yeah, it seems like the biggest issue so far, since players could use it to recognize NPCs' illusion spells too easily.

But honestly, even without any special rules like this, an illusionist who casts while in clear view of their enemies is a moron. Any adventurer worth their salt is going to see the guy in robes wiggling his arms and know something's up. The best illusions are cast from cover (which reminds me that cover should affect this rule somehow--not sure exactly how yet).

Right now I'm leaning towards only offering the option of recognizing spells to players who specifically ask for details about the spell an enemy is casting. Particularly savvy NPCs would do it too, but it probably wouldn't help so much except in the case of illusions. Thoughts?

EDIT: By "know something's up" I meant know that an illusion was likely cast--a character might still be subconsciously fooled by the illusion and have to overcome it with a save, but they would know they are being fooled. This is like how you can still see optical illusions even though you know they're illusions. Sorry if I wasn't clear enough.

[Tanarii]

But honestly, even without any special rules like this, an illusionist who casts while in clear view of their enemies is a moron. Any adventurer worth their salt is going to see the guy in robes wiggling his arms and know something's up. Oh Lordy, now you've done it. Hope you're prepared for the storm of objections coming your way. :smallamused:

[RickAllison]

Until they approach closer and hear the music accompanying the waggling wizard...

"You put your left hand in and you shake it all about. You do the Hokey Pokey and you turn yourself around; that's what it's all about!"

[WarrentheHero]

As a DM, I have a few conditions in this:
If you have cast the spell (that is, if you know the spell/have it in your spellbook), you can identify it immediately.
If you have it in your spell list, you can make a check.
If it's neither, you can't.

This is based on witnessing the effect of the spell though, not the somatic, verbal, or even material components. So cone of fire = Burning Hands if you've used it. You are familiar enough with "cone of fire" to see it and know it; you do that. To a noncaster, it could just be a fire spell. If it's in your list but not your spell, you've heard of other casters of your type using that effect, but aren't familiar enough with it yourself to know it. Maybe youvr seen kt during your trsining, maybe you produced the effect by accident while practicing a similar spell once. It becomes a knowledge thing; make a check. But if you aren't a caster, you don't have enough magical knowledge to properly figure that out, unless it's been a crucial event to your character("This scar was given to me by Fireball!" or "The BBEG has a spell that that drops lethal gas into the area, I think it's called Cloudkill.")

[eastmabl]

"Trained only" is a mechanic that is best left in 3.x. As a previous poster said, anyone can try anything - proficiency just means that you're better at it.

If you're afraid that the barbarian with the intelligence of 8 is suddenly going to start recognizing spells because he can roll 16+ on a d20, try some of the following things:

1. Disadvantage. If a player doesn't have something in his background that is magical training of some kind (a full spellcasting class, proficiency in the Arcana skill, a feat like Magic Initiate), then it's well within the purview of the DM to impose disadvantage on the roll. Why? If you would be unlikely to stand a chance of recognizing it in perfect conditions, it should be more difficult to recognize it during combat situations.

2. Link it to the action economy. If you want to determine the spell, you have to use your Reaction. By losing the ability to make a reaction like an Opportunity Attack, not every player is going to be throwing a d20 in vain in the hopes that they'll figure out what the spell is.

Of course, that creates issues for counterspell --- but a character with counterspell is not who you're as concerned about. Just allow counterspell to be cast as part of this Reaction.

[Sitri]

Illusion spells is something I hadn't thought about, and yeah, it seems like the biggest issue so far, since players could use it to recognize NPCs' illusion spells too easily.

But honestly, even without any special rules like this, an illusionist who casts while in clear view of their enemies is a moron. Any adventurer worth their salt is going to see the guy in robes wiggling his arms and know something's up. The best illusions are cast from cover (which reminds me that cover should affect this rule somehow--not sure exactly how yet).

Right now I'm leaning towards only offering the option of recognizing spells to players who specifically ask for details about the spell an enemy is casting. Particularly savvy NPCs would do it too, but it probably wouldn't help so much except in the case of illusions. Thoughts?

EDIT: By "know something's up" I meant know that an illusion was likely cast--a character might still be subconsciously fooled by the illusion and have to overcome it with a save, but they would know they are being fooled. This is like how you can still see optical illusions even though you know they're illusions. Sorry if I wasn't clear enough.

But why assume an illusion spell over a conjuration when you see twitchy fingers?


"Trained only" is a mechanic that is best left in 3.x. As a previous poster said, anyone can try anything - proficiency just means that you're better at it.

If you're afraid that the barbarian with the intelligence of 8 is suddenly going to start recognizing spells because he can roll 16+ on a d20, try some of the following things:

1. Disadvantage. If a player doesn't have something in his background that is magical training of some kind (a full spellcasting class, proficiency in the Arcana skill, a feat like Magic Initiate), then it's well within the purview of the DM to impose disadvantage on the roll. Why? If you would be unlikely to stand a chance of recognizing it in perfect conditions, it should be more difficult to recognize it during combat situations.

2. Link it to the action economy. If you want to determine the spell, you have to use your Reaction. By losing the ability to make a reaction like an Opportunity Attack, not every player is going to be throwing a d20 in vein in the hopes that they'll figure out what the spell is.

Of course, that creates issues for counterspell --- but a character with counterspell is not who you're as concerned about. Just allow counterspell to be cast as part of this Reaction.

I like these ideas

[eastmabl]

I like these ideas

I find that the Advantage/Disadvantage mechanic is often overlooked in 5E - especially when searching for a homebrew patch.

As a DM, it's probably easier to say "it's the rules' fault that you can't try this check" instead of "it's my active decision that you're probably going to fail this check."

[gfishfunk]

In keeping with the theme, a check against Illusion spells failing by a certain amount could give you the wrong information. As in, you identify it as a different spell entirely, not just 'you don't know what spell it is.' This works better if the Arcana check is made by the DM secretly, of course. As a player, I'd be rightfully suspicious if I rolled a 2 and the response was 'you recognise the spell as a high level Conjure Celestial,' or whatever. Note that this means that all of the checks would have to be made by the DM in this case, otherwise the DM making the check might as well be a sign saying 'ILLUSION SPELL BEING CAST' which kind of defeats the purpose.

Actually, a great response for a failed check would be "You recognize the spell being cast as an illusion spell," which would then make the PCs automatically suspicious of everything.

[eastmabl]

Actually, a great response for a failed check would be "You recognize the spell being cast as an illusion spell," which would then make the PCs automatically suspicious of everything.

I like this idea, but in the "failed by more than 5" sort of way. Once the players are hip to "failure is illusion," use a d8 to generate the wrong school of magic.

A roll like this would also be an excellent for a secret DM roll, as a player will know whether his roll was successful or not.

[Trasilor]

I don't like this idea at all.

It effectively gives two saves vs Illusions.

Plus, combat is supposed to be a chaotic, crazy mess. Nobody should be able to just stand there and watch their opponent cast a spell and then try and figure what school it belongs too.

Also, other than illusions, does it actually matter?

[Dalebert]

Also, other than illusions, does it actually matter?

I think folks want to avoid wasting a Counterspell on a cantrip or some such. I agree with you about illusions. Phantasmal Force already allows a save to resist and then as many investigation checks as you're willing to try to nullify it. It gives me a headache to think of it having yet another opportunity to be a complete waste of a spell slot. Still, you likely shouldn't be using it on particularly intelligent opponents anyway and those are the ones who'd be attempting an arcana check.

I'm of the mind that this should be at a minimum very challenging to do if not completely impossible. It's enough that casters effectively announce they're casting a spell without people having foreknowledge of the spell before deciding how they're react.

Spellcasting happens VERY quickly. I've heard people say it takes 6 seconds to cast a spell. That's not accurate. It takes as long as it does to swing a sword or fire a bow, i.e. it's one action; not one turn. A character moves, takes an action (maybe cast a spell), can also take a bonus action and then also interact with an object in 6 seconds. A one-action spell is FAST. "Gobbledy-gewck" *finger waggle* BLAM! It generally uses your action to choose to make a skill check. There are exceptions in cases but I wouldn't make this one of them.

If you're in a fight and expecting it to be a challenging one, e.g. one with an enemy spellcaster, then whatever they're casting is probably going to suck for you so just go ahead and counterspell it.

[Trasilor]

I think folks want to avoid wasting a Counterspell on a cantrip or some such. I agree with you about illusions. Phantasmal Force already allows a save to resist and then as many investigation checks as you're willing to try to nullify it. It gives me a headache to think of it having yet another opportunity to be a complete waste of a spell slot. Still, you likely shouldn't be using it on particularly intelligent opponents anyway and those are the ones who'd be attempting an arcana check.

Why stop with spells? Why not allow the super intelligent to anticipate the attack of a swordsman or bow user. Why not allow those with super senses (high Wisdom) the ability to perceive all sorts of body movement to help dodge attacks? Because the game is not designed that way. At least not directly. You could create a feat which replicates these abilities - effectively adding a person's X modifier to Y. But that gets can get all sort of 'wonky' with bound accuracy.



I'm of the mind that this should be at a minimum very challenging to do if not completely impossible. It's enough that casters effectively announce they're casting a spell without people having foreknowledge of the spell before deciding how they're react.

Spellcasting happens VERY quickly. I've heard people say it takes 6 seconds to cast a spell. That's not accurate. It takes as long as it does to swing a sword or fire a bow, i.e. it's one action; not one turn. A character moves, takes an action (maybe cast a spell), can also take a bonus action and then also interact with an object in 6 seconds. A one-action spell is FAST. "Gobbledy-gewck" *finger waggle* BLAM! It generally uses your action to choose to make a skill check. There are exceptions in cases but I wouldn't make this one of them.

Yes I agree. Hence why I think this is a generally poor option.



If you're in a fight and expecting it to be a challenging one, e.g. one with an enemy spellcaster, then whatever they're casting is probably going to suck for you so just go ahead and counterspell it.

Except the OP stated that you would know the school of magic, not how powerful of a spell being cast.

[Sitri]

I was thinking to know the spell all together. It's a legacy usage of the skill. My last game group didn't even know that wasn't RAW any more.

[mephnick]

Got nothing to do with counterspell for me. I've never used spellcraft for counterspelling, I use it to determine if I know why the fighter suddenly seems so lethargic so that I can find a solution next turn if I need to.

I do agree it could hurt illusionists unfairly though.

[Dalebert]

Got nothing to do with counterspell for me. I've never used spellcraft for counterspelling, I use it to determine if I know why the fighter suddenly seems so lethargic so that I can find a solution next turn if I need to.

That's reasonable on a case by case basis but that sounds different. That's recognizing the effects of a spell in action vs. analyzing the casters words and gestures to know what they're casting. It's strongly implied that everyone casts spells differently. It costs wizards 50gp per level to experiment, translate, and come up with their own version of a spell every time they learn a new one.