Game Design: Why the d10 is actually bad for Ars Magica

Games Discussion Ars Magica
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Given that spell levels jump at multiples of 5 (ignoring lower-level spells), Ars Magica's stress die (let's ignore the simple die) is too small. There is only one spell level in which the die makes a difference.

Consider for example a magus with +20 to his spellcasting roll, who is attempting to cast a level X formulaic spell. If X = 20, the die doesn't matter: he will essentially always cast it without fatigue. If X = 25, the die matters: he has about 50/50 to cast it with and without fatigue. If X = 30, the die doesn't matter again: he will essentially always cast it with fatigue. If X = 35, the die doesn't matter again, as he will fail to cast the spell.

The chance to botch or to have the die explode changes the math slightly, but only slightly so I'll ignore that.

This problem is even worse for fatiguing spontaneous magic, where the die is divided by 2 so it sometimes, maybe, adds a single magnitude.

Contrast this with how the stress die works for Abilities, with a 3-point increment per difficulty step. Consider the magus with +3 to his Concentration, attempting a stress Concentration check with Ease Factor X. If X=3, he will essentially always succeed. If X=6, he will succeed on a roll of 3-9 so 70% of the time. And so on, so that the chances of success are approximately 100%, 70%, 40%, 10%, 0%. This is a nice, gradual, spread, that allows for SOME chance of failing and of succeeding across three difficulty steps. So there are tasks that are difficult but you have a good chance at (70%), and ones that are more difficult (40%) or even far-fetched but still possible (10%) – this is a good spread of chances-for-success to work with.

One solution to this issue is moving to Arts as Abilities, i.e. using the Abilities XP pyramid scale for Arts, but also to (magnitude x 3) for spell levels. Which leaves magi's power-level pretty much unchanged, but does suddenly offer more gradations in chances to cast the spell. But doing x3 math is much more difficult than doing x5 math.

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If x=35, surely the +20 succeeds on 6+? That puts the total at -9 which is succeed with losing a Fatigue? That example is one of those when the die does matter. Losing fatigue is a big deal in some scenarios!

But sure, it doesn't matter much to that casting total. But what about 15-19, or any of the other numbers it could be? It doesn't matter to every casting total, but it matters to some. Same with abilities. If I'm at stress die+8 then for EF 3, 6, and 9 the die doesn't matter then either, and 15 is rarely going to succeed, and if I spend confidence then 12 is also basically guaranteed. Stress+1? 9+ is now getting closer to impossible and 12 is only possible with an explosion, and can't be 5 or less getting doubled, so it's not even good odds then!

The die is not hugely impactful every time, but there are plenty of rolls made by characters where it does matter, and times when it is meaningless, especially if a Simple die, both on the Arts and Abilities scale. And there's always Penetration.

Perhaps changing magnitudes to x3 instead of x5 would make it matter more often, perhaps it just makes more spells completely out of reach. Lab totals being 3 abilities (2xArts and MT), or more if a verditius, would buff lab rat enchanter and they are already very strong. I'm not particularly convinced by the argument put forth thus far, but further examples could help.

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You need to think about what role you want the dice to play before you can make a statement on whether the die size is “too small”.

It is indeed small enough that when it comes to the casting of hermetic spells, time spent in preparation and study matters a lot more than random chance. Perhaps this is in fact… Good?

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Right. So there are two spell levels where the die matters: one where there is a 1/2 change to cast with fatigue and a 1/2 to cast without it, and another spell level where there is a 1/2 chance to cast with fatigue and a 1/2 chance not to succeed to cast.

That's still not a very good state of affairs.

It matters too rarely IMO, and even when it does matter it matters too binary. I want things more gradual - to have a spell that you MIGHT pull off, but it's a long shot (10%); or to have a spell that you'll probably pull off (70%), but you might fail. And the more 50/50 option as well. The d10 dice denies us of this variety. It's essentially a binary 50% roll.

Yes, this is another major argument against this proposal.

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That isn't the issue, and stays true in my proposal. The problem isn't the proportion of arts to dice, but rather in target number jumps to dice.

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I somewhat agree with what you said. OTOH I also agree Erik’s with the binary you can or you can’t, rolling is secondary. I think the goal is not to impact easy spells but add randomness when your TeFo barely enough.

a- We could simulate Abilities’ Ease Factor by using 1d20 to cross multiple magnitude, but that results in too much penetration.

b- We could somehow “explode” the 1d10 further to make the auto-success barrier porous. I’ll explain with a TeFo score of +20 as you did above:

  • when you roll 2, you get -5. (2-5)+20 = 17, making spell levels 20/25 Fatiguing.
  • when you roll 9, you get +5. (9+5)+20 = 34, making spell level 30 non-Fatiguing and improving penetration.

c- Another approach with 1d20 is to “fold” it into 1d10 where low/high rolls get +/-5. That way, the result goes from 2→2-5=-3 to 19→9+5=14. (1/11 still doubles while 10/20 might botch)

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Again, back up - why is this “not a very good state of affairs”? Why do you think the die should matter in more cases? What improvement to the game would this bring?

(And if we're talking game design, “i would like it if it did” is not an answer. Ignoring botches and crits is also silly, they don't work they way they work by accident.)

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Having spent some time crunching the numbers on this, I’ll spare you all the words I wrote on how this would change the math. The general takeaway is that this change would make wizards better in the lab, as non-art bonuses can be stacked and are now stronger relative to spell levels. It makes magical foci worse in the lab as they provide generally smaller bonuses (compare an art of 15 now being an art of 6 for the equivalent xp - a focus provides less than half of what it would if it is doubling this, but spells aren’t half as large).

Meanwhile, it makes wizards less able to cast the spells they invent, particularly at the limit of their arts. It makes more or less all spells be cast with less penetration, strengthening magic resistance (compare the relative value of the Parma Magica before or after the change - would we make Parma grant level x3 MR instead of x5? If not, it is a lot stronger now).

If the magnitude=3 change also applied to non-hermetic traditions some of those would also be notably strengthened.

Are any of these things desirable? That’d depend on your particular design goals - but I’d revisit the assumptions that this would leave wizard power “unchanged”, it certainly would not.

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So ignore the thing that is specifically designed to make spell casting risky?

I will ask what many others have asked. Why? Thematically, magi are meant to be powerful. They are meant to be intimidating. They are meant to be able to believe with supreme confidence they will achieve with magic what they set to achieve. Would Gandalf flub casting a spell, Nightingale?

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Spell casting rolls are also affected by Aura stuff, which can make a roll riskier by introducing more botch die, and change the difficulty of the roll with flat penalties and bonuses. They are another thing that would have a greater impact if you changed Arts to the ability scale. That -(3xAura) Divine penalty to spellcasting (and not items!) is a lot ruder now, so Jerbs have just been hit with a hammer.

Spell design for Magnitudes being 5 also means you get 5 “free” points of stuff, but 3 would obviously change that. Image of the Beast goes from Level 5, 1st magnitude, to Level 9 which is 3rd magnitude, it’s now a level 15 spell equivalent. Low level spells become harder, higher level become easier (apparently its around 4th magnitude they even out and then from 5th onwards they get easier)

This is seeming to be a more and more spurious declaration.

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Why are we rolling to see if the spellcasting succeeds at all? I think it's fun to have uncertainty. But as-it-is, this uncertainty only exists in a very weak sense. I think expanding that uncertainty to cover more spell levels would make spellcasting more exciting.

And that it is more fan to increase in power gradually, from not being able to cast the spell at all, to being able to cast it rarely, to casting it usually, to casting it virtually always.

It is fun to have different gradations of chance of success, just as it is fun to have such gradations for Abilities.

In the current mechanics, the die roll is usually pretty pointless except to check for botch and exploding (which I don't suggest we'll change).

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Well, compare this to changing the XP scale to Abilities, and keeping the spell-level as-is.... compared to that, yeah, I think magi's power level is kept fairly similar to current levels.

There are changes, for sure. And other rules would need to be changed, or at least re-considered, yes. This is a massive change to the rules. But when the dust settles, the power level of magi remains fairly similar.

I think most changes are for the better, actually. For example, being able to learn spells that you cannot cast is a GOOD thing IMO. It means you can hoard bonuses or spend vis to cast the spell if need-be, which is cool. It means you have great chances to cast spell with fatigue, exerting yourself to cast the spell.

The two things I think are bad are increasing the value of Magic Theory too much, and increasing the power of magic items too. This may be enough to shelf the idea - or may be resolved by other tweaks to the system.

Regardless, this suggestion is not the main point of my post. I'm thinking more about whether the d10 is indeed a bad dice for the game as-is.

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The first quote here is more or less the first time you have actually tried to argue the design question. It would be profitable for your argument to try to unpack this further.

If you are wanting to discuss whether the d10 is “bad for ars magica”, you would need to argue that more uncertainty in spellcasting in more cases is desirable, and/or that less uncertainty is bad. Why is more uncertainty more exciting, in your opinion? What gameplay does it enable? How do you imagine it would change the feel of the game?

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I would have to say that uncertainty is always more exciting- just look at the Hindenburg. I mean why use good old reliable helium when you can push performance and introduce a bit of risk, it makes things exciting!

I think the answer here is similar- we need an optional mechanism which can magnify both the potential gains and risk for those who want a bit more “excitement”, like maybe being able to roll multiple d10 and add the results but a botch on any of them means a botch all around, and the number of botch dice used equals the total number of d10’s used. Exploding one of them only explodes the one die. Exactly how to trigger this “benefit” is another question, and should probably have some related limits (like number of d10’s being limited to a skill level +1)

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If I understand your point correctly, you’re not actually arguing that the d10 is bad. You actually think it’s good for non-spellcasting rolls, but it’s bad for spellcasting because it doesn’t have a wide enough spread.

Most of the conversation in this thread seems to be about making spellcasting use the same scale as non-spellcasting. But I’d like to propose an alternative:

If the die is too small to provide the range of results you want, let’s use a larger die. What if we rolled a d20 for spellcasting instead of a d10?

This would make the die roll more important. It would also extend upwards the range of spellcasting. Formulaic spells would gain more Penetration. Spontaneous spells would become more doable. Botches and exploding dice would happen less frequently, assuming they occur on a 1 or a 20.

Just an idea. Personally I’m fine with the system the way it is, but using a larger die for spellcasting feels like an easier fix than modifying all the rules for magnitude and such to bring Arts down to the same scale as Abilties.

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Yes, that can work. I'm not sure if a d20 or d15 will be best. But d15s are rather hard to find, outside a computer...

As you say, this change too will have ramifications outside of just increasing randomness, but perhaps good ones.

It isn't a dealbreaker, but I think the game would be better if we had two or three spell levels we had a chance to cast (or cast without fatigue), rather than one.

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However have you considered a D12? Far more commonly available, and a Platonic solid..

And in the medieval world 12 was kind of common value to use.

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How do you make that work in practice? There will be a bunch of spells a character can cast. If ball of abysmal flame is in the rarely succeed category, the magi would just use Pilum of Fire, until they got better.

The spell stuff is just more obvious. There are experienced characters who will be adding +9 to a roll. Do we get bored that the +9 swim guy always can cross a lake? No. The point is with a skill, you can go extreme. The character could try to swim the English channel. One can’t try to cast a +35 damage Pilum.

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Absolutely! People don’t learn or invent spells they have a <50% chance of casting, they stick with the spell they can do reliably until they can cast the next big thing and then invent that and cast that instead. No one is inventing Ball of Abysmal Flame if they can’t reliably cast it because that season is better served studying to increase your Arts until you can cast it reliably, why would you waste your time inventing a spell you can’t use?

People design spells they can cast, they don’t design lakes they can swim across or swordsmen they can bop on the head. Because you can pick the level of the spell when you design it, you always pick a thing you are capable of.

Yeah! Hermetic magic is reliable and formulaic spells do one thing. A +15000000 roll on your Unseen Arm casting roll doesn’t make it turn into an Unseen Porter that can lift 100 things (unless you're sponting, I guess), but a +1500000 roll on your Finesse roll on your Rego Craft magic means you just made the most perfect sword that ever existed with all those extra flourish points or whatever.

Abilities and Spell Casting are just different beasts, used differently, with different concerns for each.

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In fairness I once had a research character pursuing breakthroughs with a really high MT skill who wound up creating several spells she couldn’t use outside of a lab (with a high aura bonus) She would have loved something, even with risk involved, that would allow her to actually cast those spells in an emergency (especially if it tied to magic theory!)