A magus invents a spell in a season. Can he spend the 2xp of exposure towards mastering the spell? I very much think so; in fact, it's probably the most natural way to spend those xp.
A magus invents a spell in three seasons. Can he spend 5 of the 6xp of exposure towards mastering the spell? The problem here is that he's accruing xp in the first two seasons, when he still does not quite know the spell. Of course, there's the precedent of Parma (on which you can spend xp before "really" learning it), so I'd be inclined to allow it too.
A magus invents a spell similar to one he already knows. Can he spend the 2xp of exposure accrued while inventing the new spell on mastery of the old spell? I'd be inclined to allow it, since the magus is effectively exploiting his knowledge of the old spell in the process of inventing the new one (thereby gaining a lab bonus).
Per the rules, the only limitation to exposure XP is the absence of other XP mechanisms. Sorry invention is explicitly mentioned. That only leaves plausibility arguments that convince you and your troupe.
I have no arguments against your reasoning. Are there risks you foresee in allowing this?
I agree with Tjenner.
The first and third case I think, are completely uncontroversial and have marginal impact too. It is only two xp, and I do not think we are ever well served by quibbling over two xp.
The second case is somewhat less uncontroversial, and it is six xp, which is somewhat more worth quibbling about. It means that the spell is learnt with mastery from Day 1, without any field experience whatsoever. Had it not been for the flawless magic of some magi, I would have thought twice about that. As it is, it is a relatively rare case with only marginal impact.
I don't see them, but that's why I was asking!
@loke I am always wary about saying "it's only 2xp" - because it may be only 2xp, but it creates a precedent. Besides, it's 2xp in Spell Mastery, which is among the most "valuable" xp out there.
It is only 2xp, and mastery goes in units of 5xp. The magus would have to spend a season of practice or field practice to make a difference. At the end of the day, the 2xp is only 2xp saved for use on another skill at the next adventure when the spell is used. But I largely agree, and it is an important reason to say that the second case is more controversial. In the second case it really makes a significant difference to the advancement speed.
I'd say you can't begin to master a spell until after you know the spell in question.
So no exposure xp in mastery from inventing the spell in question.
That being said, it is not worth fighting over where you can assign a mere 2xp. You still need an extra season of something to actually get a score of 1 in the Mastery ability.
On principal I want to say "How can a magi master something he doesn't know?" but then, if someone has spent 9 months inventing a spell, it doesn't seem wrong to suggest he knows it very well.
I'd allow it. And also I'd support the early comment about it's only 2 XP. If you say No, is the argument worth it? Also that overpowered flawless magic feat exists, so lets get some mastery XP in there for other magi.
How would you handle it for someone who has Flawless Magic? Would they still get 5 'free' XP into Mastery once they finish researching?
Would the 2 Exposure XP be doubled to 4?
Why not? Flawless magic is an independent matter, so I think yes and yes is obvious.
Per the rules:
Exposure experience from lab work can be spent towards Magic Theory, Exceptional Abilities used, Arts used. To use your spell mastery in your lab work requires the relevant specialization "Lab Mastery" which is available to the Cult of Mercury only. If the character has that specialization, then he can improve his Spell Mastery in his already mastered spell by researching similar spells.
Note that I may be open as a storyteller to giving spell mastery xp as exposure on the actual spell being designed, but that's essentially a GM call and house rule at this point. (Edit: and I would rarely, if ever, as a player, consider spending my exposure on something else than Magic Theory).
Indeed, but not exclusively, by my reading of exposure: "learn simply by being exposed to the thing to be studied". Those are meant to be examples, just like Labwork and Craftwork are example activities, and certainly not the only situations in which one may benefit from exposure xp, E.g. in both cases I'd allow exposure experience to go to Leadership, if multiple characters collaborate on the task.
But you see @loke , completely uncontroversial is something you rarely see on a forum
On rereading, the book does say possible exposure, and does say all you have to do is to consistently use that ability throughout the season. Sounds like it can be used to justify almost anything, so long as you have a hobby that doesn't require more than an hour a day.
I would say yeah on this. I mean you studied the magic during the period and so the XP can go to it. I think storytelling connections work a bit more than mechanical restrictions, so in this case you studied and thus improved.