Mostly, it's a balance concern I'd say. Magi are already extremely powerful because their spells can end fights before they've even truly begun. And Fast Casting gives them a second chance to 'win initiative' and level the opposition. So mundane efforts to stymie a magus have a good chance of eating arcane fury even when they go first. Even against stronger, supernatural opposition Fast Casting still gives mages a powerful chance to get off additional spells in a combat round. Basically, it's just a significant power boost across the board.
Except when you're against other magi. They also have the option for Fast Casting, and it's here the rules shine as a creative way to simulate extravagant spell duels while helping to prevent mages from being obliterated out of hand just for losing initiative. It also gives mages a framework to employ their magic in "Oh no!" situations (like being caught in a rock slide) - where it's clear that there's very little time to act, but simply allowing mages to do their thing might make things too easy; it simulates high pressure casting where there's a greater chance to mess up.
Basically, it's not a problem against spell flinging opponents and environmental hazards. It's against the non-spell flingers (and especially the mundane opposition) where Fast Casting has the potential to be truly unbalanced: it makes the gap between mages and not mages even wider than it already was. And the only tool the rules as written give you to balance that is how restrictively you interpret what a suitable time to allow Fast Casting is.
I'm going to have to ask you to cite the rules where Fast Casting is explicitly called out as being instead of your normal turn. Because I can't see where that's even hinted at. Do note that you can fast cast multiple spells a round if you're quick enough / roll well (example goes up to three spells a round with provisions for more), so it's not simply a case of implicitly taking your turn early.
EDIT: further research settles the debate cleanly. Found this buried in the combat section:
Its this bit that causes the contention, as it is unclear what is allowed to trigger the immediate response. If the clarification is that the fast cast can be in reaction to anything, then all good. Just so we understand.
As I noted above, it's not all that proscribed! Mostly up to the SG I think. The relevant text for consideration on pg.85: "A maga may choose to cast a Spontaneous spell extremely quickly, as a response to an attack or other surprising event."
So at the very least, attacks are covered (though not, specifically, attacks on your person - you can probably cast in defence of someone else too). And then 'other surprising events'. I figure that means things like rock slides, or rapidly approaching donkey carts, etc. Mostly going to be case by case it seems - especially outside of combat.
It would seem to me that if you cannot fast cast and cast a regular spell, and a regular spell is a standard combat turn option, then you cannot take a standard combat turn option with a fast cast spell.
Until now, I had thought that "reaction" was the only area that there was any debate.
Turns out I was wrong.
A lot will depend on who is running the story and how they want to pace the action. But as far as I am concerned, if I am running an action sequence, then the answer to "reacting to what?" is anything at all. A flinch, a sneeze, a sudden movement, the clouds parting, the count of 3, anything.
Granted, I am liberal in my interpretation and consider myself quite handy in running action sequences.
What has me surprised here is the confusion caused by a very straight forward application with no tricks.
I am not trying to change or reverse any decisions. I am quite pleased the way things are. The one who runs a sequence needs to have room to make fiat rulings and do so quickly. The wrong decision is better than indecision. And if I am going to play a character, then the SG needs to be secure that I won't overrule them. But I do want to be allowed to voice my opinion.
It really depends on how you are applying the "or" in the sentence. Does the phrase "cannot cast" or "cannot cast more than" apply to the phrase "or a fast-cast and a normal spell?"
I believe Asilano interprets the sentence as meaning:
Thus, a magus cannot cast more than one normal spell in the same round.
or
Thus, a magus cannot cast more than a fast-cast and a normal spell in the same round.
while silveroak interprets the sentence as saying:
Thus, a magus cannot cast more than one normal spell in the same round.
or
Thus, a magus cannot cast a fast-cast and a normal spell in the same round.
The first says that you cannot cast more than one normal spell in the same round. The second says that you cannot cast more than a fast-cast and a normal spell in the same round.
Thus, you cannot cast two normal spells in the same round. Nor can you cast two fast-cast spells and a normal spell in the same round, nor a fast-cast spell and two normal spells, in the same round. You can, however, cast as many fast-cast spells in a round, as long as you keep making the roll at a cumulative -6.
I wouldn't have, either...mainly because I don't have it and it's not on my "must-have" list.
Thanks a lot to trogdor (and Peregrine too!) for all the awesome work he did on the wiki. It has been much improved by all this, although we'll have to be careful to link future characters in all places.
I thought once you were right, in intent if not in deed, but Lord of Men convinced me otherwise. You choose to consider any comparison they make between fast-casting and delayed actions as, at best, working only in one way, but if you don't, Marko clearly appears to be in the right.
Very good point.
So if you're a mundane facing a magus, be quick, or be dead.
Or just ensures s-he doesn't see you coming.
I think that, at the very least, this covers game actions. Anything that would take a character a combat round, from attacking to walking to casting a spell...
But I can also see it applying to shorter actions, like when the duke's seneschal wants to tell him the name of the spy you planted at his court and you try to fast cast a PeMe spell to erase his memory.
I'd quite like to give Antoine a familiar, both as a forge companion but also possibly as a character that could accompany others on short adventures when Antoine is reading (I don't know if that's something any familiar would do, of course). Would someone be willing to run a story to find one, or to add a sideline into another story Antoine is part of (currently just Waddenzee, when Carmen et al head off)? Antoine's currently free all of 1238, 1239 and 1240; he's probably just going to be reading most of the rest of those seasons (books on Arts mostly, and the Valdarian cult book he brought).
The core indicates that a magus should be able to find an animal that suits his best arts, so Antoine would be looking for a creature aligned with Rego Imaginem; although Muto and Mentem are close. Since he wants it to help in the lab, having an intelligence score would be a bonus. I'm not sure what animal would fit those constraints, though - I'm hoping the troupe has some ideas?
What about some kind of homonculus? Or a human-like plant, like mini-groot?
Thinking: ReIm => Fae, thus human. MuMe => Human.
=> Magical human => Magical human-like being => baby groot, which also looks fae.
