How long to cast a spell.

Hi all,
I've been lurking for a while, and as my gaming group is just now starting to play an Ars campaign again, I though I'd impose a question on you good and wise folks.

My question is this: How long would you say it takes to cast a spell? I know it's "about" 6 seconds, but do you start casting before the first person goes and continue until it's your initiative and then do nothing until the beginning of the next round?

The reason for this nit-picky meta- game question because one of my players wants to design a spell to interrupt another wizards spell without actually knowing what it is.

Specifically, he's looking to cast a Perdo Mentum spell to make the person forget what spell they're casting, or a Perdo Imanginum to make they not be able to speak a few crucial words.

This brings up several questions. Is such a thing even possiable? I'm not even sure it is, although logical, it gets around all the counterspell rules. True, it does have to penetrate their resistance, which is the only thing stopping me from ruling it just plain too powerful.

So if the enemy wizard is casting, and you go before him, can you just cast this spell and (assuming it penetrates) foil their spell since he obviously is in the middle of casting by the time you're done. Can you fast cast this effect if you go after the enemy wizard?

Is Momentary duration on "forget what spell you're casting" long enough? I'd guess so, since the rules say memories don't return when detroyed. And just how long is "momentary" any way? There are some references to meta-magic spells with momentay durations being able to affect the next spell you cast, basically 6 seconds later. If all this is ok, is the enemy wizard basically unable to cast a new spell till next round?

I'm tempted to rule that such a spell simply gives the caster a reduced casting total, or requires a concentration roll from him, or perhaps extra botch dice, but I'd like to hear what you all say.

Thansk for your time,

Tim Reynolds
Storyteller: Silex Duras Campaign

Hi Tim,

Great to have you onboard!

I'm on European time so here it is 2.30 in the morning - and I ought to have gone to bed ages ago... Therefore the rather short answer for now, but I expect others might return a more fullfilling answer - if not, I'll return later during the weekend.

My own presumption is that casting a spell is something that comsumes all of a given round - but I'm not sure this is actually explicit in the rules. A few thoughts come to my tired brain; first of all what your player is aiming at seems to rest crucially upon the rules for fast casting, in most cases anyhow, and to fast cast a Formulaic spell the magus would just have to train spell mastery with the spell to get the possibility to fast cast it. The fast casting would simply lead to an initiative sum being compared between the two. I would reckon that a momentary spell would only prevent the other from casting spells for one round - my imidiate reasoning tells me that those guidelines for certain Vim effects are special cases and not momentary duration generelisable. I don't think using PeIm would neccesarily make it impossible to cast spells only make it much harder (look to the guidelines for casting without sound) and if you haven't seen it there is actually a spell somewhat to this effect in the core book - only done with ReIm. The idea of concentration roll and added risk seems like a good way to go - concerning the destruction of memories, it very well might make the person forget the spell he had decided upon but the situation might very well make him come to the same conclusion regarding what spell to use. Whether PeMe can actually destroy the knowlegde of the "skill" of how to cast a certain spell is another thing. Even though it might belong to the Form of Mentem I'm not convinced that you can destroy abilities like although you might categorise them as a sort of memories. If you allow PeMe to destroy skills I would at least demand the spell to have a duration - that skills would otherwise, as emotions, return at the end of the magic.

Two times food for thought:

A) if he intends to affect another magi with these spell he has to remember that they'll probably require quite a high Penetration and if he intends to fast cast them his Casting Total might be further diminished, and thus also his Penetration, so they shouldnt be to high level spells if possible. Second having both, or more, Formulaic spells might give him and extra edge because variant opponents might varrying Resistance to various forms - having more than one version should make it more plausible than one them might actually penetrate.

B) since he is thinking of engaging other magi this might not be an issue at all - but keep in mind that even a simple skirmish between magi would be sure to escalate to a death penalty, if not during Wizards War or March or simply kept secret...., if such spells where to be used. Trying to rob a fellow magi's ability to do magic impairs the maximum sanction from the Order - and even though this is only very temporarily the case might thusly be argued against the magus in question.

I would, like Furion, use the fast cast rules in order to interupt a spell being cast.

For an "in game" answer I'd say that the length of time to cast a spell varies significantly spell to spell, caster to caster and even casting to casting so it is tough to predict how to use a spell on someone. This way you can perhaps head off some future exploitation of the way that the game uses episodic instantaneous actions to model continuous time (because it's not inconceivable that you players will want to do this in some other way as well)

Thanks for the welcome, and the delicous food

He's on about this because while claiming our new covenant he had to fight ghosts (or alterations) of magi who cast spells like they did in life. But you're right, such a thing is unlikely to happen often in a normal adventure.

Hmmm, I wonder if interupting the use of Might is something Hermetic Magic can do, directly instead of countering the effect. Or draining it.

Thanks again!


It wouldn't by any chance be Calebais...?

No, it's not, but I'm sure that adventure was lurking in the back of my mind...only steal from the best =)

Many moons ago, I had that adventure, and ran it under god-know-what edition, but it has long since disappeared along with my Bunnies and Burrows rules, and all my Champions stuff, hehe.

Is there a current version of Calabais for 5th? Is it worth getting for rules or anything? Most of these players would have played it umpteen years ago (Along with Stormrider), so I would unlikely use it again for an adventure.

Indeed it does - and I think it's kinda nice that oldies keep coming back!

Well with this in mind I think that the spells would have to be a bit different. Depending on what you ghosts are like of course, but if their magic is now fueled by their Might I would personally argue that PeIm or any other magic to influence the sounds or gestures of the ghosts wouldn't have any game mechanic influence since in essence if they are using their Might it isn't really Hermetic magic anymore. I haven't gotten all through the TMRE yet so it might contradict me in this regard. I stress mechanic because is could see plenty of roleplay consequences of using such magic on the former magi's ghosts and that might turn a battle in favor of the characters as the ghosts might be genuinely baffled or not themselves believe in the strength of their magic without sounds... But wouldn't let said mortal hermetic issues affect the mechanic performance of their might fueled magic. I would also add that if they are spiritual creatures of Might the magic that could affect them should probably be fixed to a specific defining Form (in this case Mentem seems the obvious candidate).

For more of this you might be interested in this earlier thread Hermetic Ghosts - which is of course quite biased by the same of my thoughts.

And btw - magic isn't green! It's the colour of ... (sorry, not at liberty to tell)

I agree - and I must admit that too often this concept of episodic instantaneous action brought on by roleplay mechanics too often might have had me forget that truth. A bit sad bc it robs many opportunities for interesting scenes and descriptions away.

Wow, great info.

Just for clarification, these creatures seem to be ghosts, but they are actually Alterations left behind by the Cult of Mercury long ago, and since addled by the Dominion caused by building a church on their old ... erm...haunts.

Mirth and Kevin Matchstick would disagree with you about the color of magic.

Love the "magic is tricky" response, thanks alot guys.



to find rules answering your questions, you should look up:
ArM5 p.174 with the rules for Initiative when casting spells.
ArM5 p.83 for Fast Casting.

From this you can see, that ruleswise it is just a matter of Initiative which magus' normally cast spontaneous or formulaic spell goes first. Casting duration does not figure into it - unless one is taking more than one action to cast - e. g. by casting ceremonially.
If your magus wishes to make sure that his target really is casting a spell before casting his PeMe spell onto it, he will need to Fast Cast his defense.
In that case he should master his spell for Fast Casting (ArM5 p.87) - spontaneous Fast Casting will likely not penetrate.

The spell your magus wishes to use would be:
Distracting the Caster PeMe 10 (R: Voice, D: Mom, T: Ind) (Base level 4 [remove an important detail from memory], +2 R: Voice).

Kind regards,


Thank you for taking time to respond.

I have read those rules, of course, but I guess my confusion is with some of the wording. Fast casting talks about the need to use it in response to "a suprising event", which with two wizards dueling, one casting a spell might not be. Initiative and magic talks about spells taking a whole round to cast (or at least 3.5 seconds, so you can't cast two in a 6 second round).

Ars doesn't use a declariation phase, but I bet most of your players ask the same question as mine all the time "What's the bad guy seem to be doing this round?" Especially if the heroes are going on a higher initiative, it often gives them a feeling of dread or accomplishment to try interrupting even their momentary goals. "Biggus Maximus is going to swing at the defenslesss maiden" so the heroes can say "Oh, well with no thought for my own safety I throw myself inbetween them" or even "We're so screwed!"

I can understand the need to fast cast a spell when you don't really know what it's going to be till it's almost flying toward you. I'm more wondering about what you can do pre-emptively. An Auram mage could wait till someone swumg a sword to spont cast a Creo Aurum spell or they could just Broom of the Winds the offending mundane if they go first. Could they just declare they're going to deflect the targets next blow with non-fast cast magic IF they go before the target?

I also understand that much of the reason is meta-game balance issues.

But overall, you don't have a problem with the idea of a spell that, if was fast cast and beat a magus's Magic Resistance, would stop any sort of spell irregardless of form?

Thanks for the help, it's useful to see how others would handle it in their campaign.


Well, if they ask, they forfeit their initiative, having waited to see what the other was doing. :slight_smile: I guess that if they have initiative, they might blindly cast a counterspell as a "normal" spell, hoping it does something useful. If they don't have the initiative, e.g. because they waited, they'll have to fast-cast.

If you wait out an event in a combat turn and wish to react to it, your Initiative will suffer. Normally a spell takes an action, just like an attack. So it makes sense to apply Fast Casting rule then, which applies for casting "as a response to an attack or other surprising event".

I believe that here you are overinterpreting the text of ArM5 p.174. You determine your normal spontaneous or formulaic spell casting in the same round where the spell goes off, and it takes you about the same time as a combat maneuver - which does not only consist of the final connecting strike - occupies a warrior.
For the rules, how long it takes to pronounce a spell is quite irrelevant. Consider that command actions for Enchanted Items could well use only a part of a second, but still you can only trigger one Enchanted Item per round. This is a strong hint, that also the impossibility to cast more than one spell per round without resorting to Fast Casting should be explained with the impossibility to focus on two full strength spells in one round, and not with any durations of spell casting.

Well, AFAICS in ArM5, if they wish to know what their opponents are going to do, they either need to guess - using player's judgement or an appropriate skill roll. Or they have to wait out their opponents - reducing their own Initiative to below their opponents'. (ArM5 p. 171: "A party with a high Initiative may delay its action to repond to a later action in a round.") In the latter case, they need to Fast Cast if they wish to cast a spell before the opponents complete their actions.

Yes, they can, by declaring to cast a normal spontaneous or formulaic spell, e. g. 'Broom of the Wind', at their Initiative, and then abort it if the attack it shall counter goes first.

No. Fast Casting a mastered PeMe 10 spell means that your PeMe casting total - 20 must beat the target's magic resistance versus Me. So the 'ifs' here are that large, and a favorable outcome that improbable, that I don't see a balance problem here.
There are indeed spells in ArM5 that come close to 'Distract the Caster', like PeCo 5 'Touch of the Goose Feather', ReCo 5 'Curse of the Unruly Tongue' and their derivatives.

Kind regards,


Quite nicely said, thank you.


I see you already got very good advice - so even if I'm more awake than last time I'll refrain from adding anything.

Except to ask whether my memory betrays me or if you didn't have some additional questions in your last post now edited away?

(maybe someone has been tampering with my palace :question: - I'm just at the moment reading about mnemonics in TMRE :smiley: )

Not to my knowledge, but maybe I forgot what room I put that in my own Palace =)

no worries - seems that I simply took a wrong turn and got two rooms/threads mixed up... :blush:

Sir, can I interest you in a fine extension to your palace - some more rooms here? Perhaps a Map installed within the palace? We have spells in The Mysteries which will do it for you in a trice...

I don't know, all these Mysteries seem kinda suspicious to me. I mean, what's with all the secrecy? We're all brother's here. Do I really have to jump into a volcano and sacrifice my pet rabbit so I can remember better?

While the art of memory is discussed in the mysteries book, it is not actually a mystery virtue and there is no requirement to sacrifice your cat to get it. (Of course most cats are self centered and cruel animals that would be well served by being thrown into volcanos but I don't have sufficient relevant information to judge your particular cat.)

I'll be jiggered, it is just an ability. I guess I skimmed over that, assuming it would be a typical Mystery Virtue.

Not really complaining, though, it's great to have new Ars stuff to peruse.

Can't talk long, cat will be back soon. He's a monster.