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,
Storyteller: Silex Duras Campaign