As discussed here, I said I wanted to make Spontaneous Magic more accessible.
Whether this is a really cool House Rule modifying Spontaneous Magic or a potential building block for 6th edition or a crazy idea that needs to be ripped to shreds and it's proposer ridiculed, I'll leave it to the community.
Spontaneous magic in Ars Magica 5th Edition is something of a bait and switch. The idea behind it is that Hermetic Magic is flexible and can do great things. In practice Spontaneous Magic isn't flexible, and it can only do great things with a lot of luck, or a lot of skill, because of dividing by 2 or 5. Ars Magica needs a system that really gives flexibility back to the players and makes Spontaneous Magic accessible to almost all magi. It needs to cost something, and it needs to be relatively reliable, but it needs to be limited, too. I hope I've struck the right balance.
Spontaneous Magic is governed by a new ability Hermetic Improvisation. With this ability magi can cast significant, if wild magics, of almost any magnitude if they know enough. The Hermetic Improvisation ability is never used in the conventional sense, but in a manner similar to how Parma Magica is used. The score of Hermetic Improvisation represents the highest magnitude (Edit:level/5) of spontaneous spell that a magus can cast. May need to consider whether Puissant and Affinity should be available this ability, but I'll leave that to the discussion.
Hermetic Magic is powerful and flexible. Your skill in this ability represents the magnitude of magic you can command if you push your limits and your knowledge. The score of Hermetic Improvisation is the highest magnitude spontaneous effect you can achieve, limited by the level of one’s Form score for a given effect. Requisites apply as well, so if two or more Forms are involved, it is the lesser of those Forms and Hermetic Improvisation. Specializations: Any Form
The maximum effect a magus can spontaneously cast is the lesser of Hermetic Improvisation and the Form of the effect. Techniques do not add to the total for Spontaneous magic as they do for Ritual and Formulaic magic. Spontaneous involves producing effects that the magus doesn’t really know, and to apply Techniques to the effects suggests some level of knowledge. It is only during a period of study that a magus begins to link the underlying effects of a Form to any applicable Technique.
Spontaneous spells are always cast, but never have any penetration. The cost for casting Spontaneous Magic is two points of fatigue, as it requires great effort on the part of the magus to control the magic. Spontaneous magic, like Certamen never creates wounds so if a magus had 4 levels of Fatigue and worked a spontaneous spell he would fall unconscious and be at 6 levels of fatigue, which would resolve as the chart on page 179 indicates. In cases where the effect causes the caster to fall unconscious, the effect does resolve.
Vis can be used in three ways with respect to Spontaneous Magic. Vis can be used for adding Penetration and vis can be used to increase the magnitude of the effect, or a combination of the two. [strike]As always, the amount of vis used is limited by one’s Art score.[/strike]The amount of vis that can be used is, again the lesser of the Form score or Hermetic Improvisation. Each pawn of vis used to enhance penetration increases the penetration by 5. Each pawn of vis used to increase the magnitude increases the magnitude by one. Vis can also be used in place of a fatigue level on a one for one basis. When using vis, one must roll botch dice equal to the situation/environment modifier + number of pawns of vis. Note, this is botch dice. It's presumed that you have rolled a 0 effectively and you are checking to see if you actually botch. Using vis in conjunction with spontaneous casting is dangerous, that's why magi learn formulaic spells.
There are some consequences to this fundamental change to Spontaneous Magic, namely two flaws: Weak Spontaneous Magic and Difficult Spontaneous Magic, with Rigid Magic having an honorable mention.
With respect to Rigid Magic, I don’t consider it much of an issue, they couldn’t use vis to boost their spontaneous spells before, so not using it now seems consistent.
Weak Spontaneous Magic says that magi may not exert themselves to cast Spontaneous Magic this suggests that they must use vis to work any spontaneous spells, since they can’t fatigue themselves. I think that’s a reasonable proposition. Although, in vis poor sagas it’s a really big deal. IMHO, the setting doesn’t suggest vis poor sagas, though.
Difficult Spontaneous Magic requires that the caster always exert himself, the only change here is that he can only substitute 1 pawn of vis in place of fatigue, not two pawns.
There may be other unintended consequences of this change. I know that there’s a virtue that allows one to use similar spells, and the Diedne virtue does have an effect with Spontaneous Magic, as well. We can discuss those situations and others that I’ve overlooked.
I don’t really have any realm interactions worked out, although the botch dice modifiers might be sufficient for that in cases where vis needs to be used. Perhaps auras modify Hermetic Improvisation directly…
Anyway, I hung spontaneous magic on an ability because that table progresses much slower. I made it tied to a Form, so that you have to have a little bit of knowledge about the Form to get the effect you want. I have made it possible to create high level effects rather easily, if you add vis, use virtues to increase the rate one improves Hermetic Improvisation, perhaps all spontaneous spells need a weird die botch check of some sort? The idea was to keep it relatively simple in play, there's still a fair amount of complexity that's needed in just figuring out the magnitude of the underlying effect, but everything else is really simple.