overlapping spelldurations/effect targeting

A magus casts a spell on human target (MuCo(An) to transform to a toad for duration diameter, then in the following round casts a spell (MuAn)(Aq) to transform from toad to a puddle of water but with duration sun. What does happen?

  1. Can the second spell be cast on the first, because the human got additionally to the human form also an animal form, or is this already not possible? (AFAIK its possible)
  2. Does the second spell stop working, when the first spell expires, because illegal target (form) for effect or does the human continue to be water until the second spell expires? (I would say the second spell overrides the first one and the effect continues to work, even though the first spell stopped, because the check for legal target is only relevant at the time of casting)
  3. If the second spell would have duration conc, would it stop after first spell ends? ( because conc effects check correctness of their target every round in comparison to duration dia, sun, moon, year?) Or could a concentration roll be necessary to maintain the spell, when the first spell expires?)

How do experieced GMs solve such problems?

My wholly private opinion on this. This is a trick to get around the magus Arts limitations. Is this the way the Troupe want the story to go?

That being said:

  1. Noble's parma, only Bjornaer transformation is Corpus-proof. So it is possible.

  2. There's no "check" time. Magic feeds itself same as the wind pushes the arrow. The fact that you need to touch the Target to apply the magic is just to start it going. The magic will fizzle as soon as the target "vanishes" because it goes out of scope.
    {Well, adding a free Corpus requisite might solve that, the same way keeping your clothes on might require some Herbam.}

  3. Mu. There's no "check" time.

There's been a few threads about this if you want to form your own opinion.

Thanks for your quick answer. Actually we have a very low leveled, slow campaign running in alps tribunal (austrian mountains). To be honest: It was just a work-around of myself, as a GM, because i did a mistake. One NPC transformed a misleaded grog to a toad for sun duration, although he couldnt do that at this moment (I miscalculated casting total with MuCo) so I thought to use the "trick" to have briefly changed the grog to animal before, since he has a higher total with animal to cast sun duration transformation.. Just thinking of an explanation, if a player would find out, that I undesiredly cheated.. ^^

But interestingly thats a way, how to stop longer lasting spells, earlier without having to dispel or use harnessed magic..
have to think about that. good nite..

The best way to fix mistake is to tell the story one step removed. What you are playing isn't "mythic reality" but only what History remembered.

So, if you screw up : "Well, we've been told that's how it happened even if it sounds impossible. Maybe that's what he did 20 years later on a similar occasion and they got mixed up. We'll have to find better sources to explain it away."

Or just acknowledge that you got the math wrong. Lord knows, it happens to me often enough...

Or do a quick re-design of the NPC, and have them be 1 year older, so that they DID have time to read through that Branch book on Animal.

Or retcon it so that the roll open-ended.

Personally, when I find that I did something wrong-but-necessary for the plot, I explicitly call it out, and then give bonus XP to the players for forcing me to do so. ("Nice job on getting Professor Doom cornered in his evil lair. Ooh... turns out he has an escape hatch right there.") This allows the PC's to try to have goals to shoot for, but also allows me (the GM) not to completely get my plot destroyed because the players were overly-clever.

AFAIK, this particular problem is not addressed in RAW.

However, my take would be that once a spell is successfully cast, it continues until its Duration expires (or is dispelled, etc), even if the target subsequently does or becomes something that would have meant it was an invalid target back at the time of casting. Certainly, if a target leaves the Range of an on-going spell, the spell effect continues to affect him (ArM5, page 111). Likewise if a target leaves a Group, then he still continues to be subject to an on-going Group effect (ArM5, page 113). Likewise, I am fairly certain that Animal healing spells (with Duration) cast on a Wolf Bjornaer (say) remain active when he switches to human form. Likewise, you don't normally get a second chance to resist something if your Magic Resistence suddenly increases while an effect is active --- lowering your Parma Magica so that a friendly effect with Duration can be cast on you wouldn't work, for example.

Also, it means that you (the players) don't need to constantly come back and re-evaluate whether effects will continue or not (so, it saves rules-handling, which is a good out-of-character reason for this choice).

So, I would say that the toad (ex-grog) indeed does become a puddle for the full Sun duration.

Of course, a target being subject to complex overlapping effects is a good reason to roll extra botch dice, if it comes to that!

I would agree with that ruling as well. HoH:MC has some info on page 22 that tends to support this: spells in effect before a Co/An transformation remain in effect, so it seems logical that a transformation expiring wouldn't necessary cancel another spell already in effect, even if it relied on that transformation in the first place. Spells like Form of the (Temperament) Heartbeast distinctly state they continue after the magus returns to human shape and, while that particular spell is tied to Heartbeast transformations in particular, I'm not sure that invalidates the precedent. If anything, since Bjornaer magi are not affected by Co magic when transformed, while those transformed via other methods are vulnerable to Corpus, it makes the point even stronger.

It seems a good rule for both flavour and game balance as well. If you could dispel a nasty effect with just a momentary MuCo(An) spell, it'd be a bit weird, especially for the PeVi specialists.