Ars Magica Spell Guidelines

[Jamey Saldana]

I started with the idea of changing a man into a horse, which is stated clearly in the gudielines as MuCo/An level 10. There is also the guideline in the Animal section which talks about adding a useful minor ability to an animal being base level 5.There is also the general spell guideline which states than a related minor power can be added as part of a spell effect by adding a magnitude (+5 levels).

The base to morph a human to a land animal is level 19, and a fish or bird is 20. This makes a kind of sense, being that it sounds harder to turn a human into a monster dolphin, than to just turn them into a dolphin. And harder to turn into a fish or bird, than a dog. And it certainly follows that turning a man into a dolphin is tricky.

Then I got into what it would take to turn a human into a Dragon-ish creature. The closest base I could find was MuCo20 for a flying creature, then modified upward for the range of fangs, claws, poison bite, gills, night vision eyes, and such that make a draconian form so intimidating.

This ends with a MuCo effect of 30 which allows the caster to tailor a wide array of abilities from a range of beasts into one form. That is the same complexity in the rules as turning a human into an insubstantial form.

A spell can change the caster into a natural land creature at MuCo/An base 10, a bird of fish at base 20. Understand you get the physical benefits of the new for, but no implied magical powers. If cast with foci you can end the spell at will.

This is where I am not sure if the effect should be +1 mag for the major change of the target creature when doing a Muto Corpus effect, or +2 mags. Is the base effect for Muto Corpus high enough to justify the alteration of the form at +1?

I'm currently DMing a play-by-post D&D 5e game. The module I'm using involves the party battling trolls in stables. Defeating trolls involves judicious use of fire damage. Stables are also often filled with (flammable) hay.

I've searched for posts regarding how to handle the spread of (nonmagical) fire, including the smoke it may generate, but have only found a few questions regarding specific spells, or this question regarding damage from one grid hex/square. Comments have additionally noted these two questions:

Although as you noted there are spells that state they light flammable objects on fire and there are spells that allow you to extinguish flames in an area (like Control Flames), there are no general rules.

This does not mean these things cannot happen. No TTRPG can truly cover every situation, they rely on varying degrees of real world 'common sense', which largely means it is left up to the DM. Throwing fireballs in a forest during a drought will likely cause some problems and spells that create water can help solve them.

Spelljammer Academy does feature a rule about inhaling smoke, but the smoke is just there and wasn't actually generated over time. Princes of the Apocalypse also seems to feature a rule regarding the inhalation of smoke but I do not own that adventure.

As a word of advice from a DM who has previously ran head first into making elaborate homebrew rules, think carefully about implementing rules like this. They take time to properly develop so before committing I would ask myself a few questions:

find what? you mean the "Cthonic magic" virtue? If that is what you mean, then I suppose RoP:I (that is: "Realms of Power- The Infernal") would be the book of your choice. But I cannot say for sure since I have not read that book and have not used Cthonic magic in my own game.

If what you want is an infernal version of holy magic, the easiest thing to do is to just copy paste the description of holy magic rename it "unholy magic" and have it do the exact same thing, but unholy.

Infernal magic
Minor/major - Supernatural/Hermetic virtue
Lets you use infernal guidelines for hermetic magic. You can use any Infernal R/D/T when designing your spells and if there are any specific magical effects that exist in infernal magic but not in hermetic magic you can use those effects when designing spells as well. Your magic counts as being aligned to the infernal for all purposes. This virtue automatically grants you the flaw "Dark Secret" for no extra benefit, as practicing magic that is aligned to the Infernal is a hermetic crime and being found out will surely result in your character being subject to a Wizard's march.

I just made up this virtue hence the unhelpful assessment as to whether it is minor, major, hermetic or supernatural. Since I invented the virtue it is impossible for me to give an accurate assessment of how powerful it is and how it should be calculated for character design purposes. That can only be decided by discussion with your troupe.

As I have need for this for a game I run, I may want it elsewhere later, and it may help others, I thought I would do a post similar to my post about Aegis of the Hearth a while back. The structure of the post will have to be significantly different, but the idea of examining the logic of what is written with extreme care is the same. I want to clear up what is actually written in the books about General spells, what is frequently incorrectly stated about them, and about what is necessarily implied by what is written. As an addendum, I will make the follow-up post about the mastery option Adaptive Casting.

Edit: As a point of clarity on other things not varying, two spells may use exactly the same guideline, maybe with different levels or maybe at the same level, with the same Range/Target/Duration and not use the guideline in the same way. If the guideline is not being used in the same way, then something other than the power is being varied, which disqualifies the spells as being two versions of the same General spell. For example, destroying Infernal Might is different than destroying Faerie Might in a non-power way, even though they use the same guideline.

My goal is merely to extract what the rules state explicitly and implicitly with as much care to the logic (which means avoiding internal contradictions) as possible. Many SGs may not like what this says about General spells. That's really not a problem. Feel free to house rule things however you want. But I do recommend listing such house rules among your house rules for clarity. Same thing with spells of intermediate levels if you disallow them.

No, as I showed above, general guidelines have absolutely no bearing on spells being labeled General spells. Not only in that direction, but I can show you examples of spells using general guidelines that are not listed as General spells.

So let's say my oldest version of Ranulf invents a spell in all ways similar to Pillum of Fire but at level 45 and having a damage modifier 25 points higher than Pillum of Fire from the core book. If he then gets a single level of Adaptive casting mastery he can use all of his Pillum of Fire spell mastery skills with the new spell.

Ignoring the question of whether Pilum of Fire counts as a General spell, my understanding is that it isn't the new spell that needs to be mastered with Adaptive Casting, but rather the original Pilum of Fire spell, which then gives its mastery to all other versions of the same spell.

However, I can quickly answer that the mastery for any one version can be used for any of the other versions. That's what it says. There is no mention of original versus newer distinction within the special ability at all.

I don't think, under RAW, varying the 'level of effect' - is enough to make them a general spell. It is, however, enough to make them 'similar spells', per the guidelines on ARM p.101, as long as other parameters don't change. In fact, I believe this is one of the key criteria these rules are designed for.

That said, I'd absolutely consider allowing a character, (perhaps one with FFM and/or Adaptive Casting), to make a Major or Hermetic breakthrough that indeed did further the 'generalization' of spells in the manner you've suggested to include similar effects. This would be a major step in 'bridging the gap' between Spontaneous and Formulaic Magic.

Per OP's argument, Wound that Weeps and Clenching Grasp of the Crushed Heart are two different levels of the same general spell. However, notably - in Darius of Flambeau, the chargen example in ARM5 - he has different mastery abilities for these two spells.

No, not at all!!! Please don't claim I said that, not even implied it. You could use exactly the same guideline at exactly the same level and still get a different spell. A conditional statement does not imply its converse. Similarly, not all fire spells that cause damage would be versions of the same General spell, even if the have the same R/T/D stuff. Now, you could make other levels/versions of the Wound that Weeps.

My thought was that if you could make other levels/version of Wound that Weeps to the point where the spell is mechanically identical to CGotCH, and were attempting to stack mastery abilities, that gets a little... rule-pretzely for me, since at that point we're getting down to the 'name of the spell'.

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