Dimicatio rule clarification

Hi everyone. This is my first question here.

I am storyguiding with a troupe that is sticking mostly to 4th edition Ars rules (we do not have a copy of the main 5th ed. rulebook) but from time to time we find ourselves trying to adapt material from various 5th ed sourcebooks for our use.

In this case, using my Normandy Tribunal book, I am planning to get the players through the Hermetic Tourney for vis distribution. Most of the events pose no problems, but I am stumped by the way to properly run the "Dimicatio".

The Dimicatio paragraph states that in order to avoid getting through the Parma, participants willingly lower their penetration (they call it effortless casting... I assume that's a 5th ed concept?). Now, I know that 5th ed modified penetration so that higher levels are harder to penetrate, but that is the extant of my vague knowledge.

I can certainly say "Okay... let's allow penetration of zero in my 4th ed group". But then, the success of the fast-cast counter to such a spell is trying to reach half the penetration of the first spell... this seems awkward and too easy, not allowing a meaningful competition; I have to assume that fast-casts work differently in 5th ed...

So, can anyone enlighten me on this topic, perhaps suggest a simple way that I could make this contest work with reasonable balance with my 4th ed troupe?

Thanks in advance for any help,

Siglorel scholae Verditius
Gatineau, Québec

Dimicatio is described on page 21 of HoH: Societates.

The attacker uses the "Forceless Casting" Spell Mastery Ability to ensure a penetration of 0, while the defender attempts a Fast-Cast Defense.

I'm afraid I don't remember the 4th edition rules very well, but aside from the inconvenience of having to learn a new mastery ability for any attack spells you plan to use, it would seem easy to handle in 4th ed.

Of course, your characters COULD intentionally cast spells with extremely low penetration and hope it doesn't penetrate...

Note that forceless casting is NOT a mastery ability, as it requires 'no particular skill or effort'; any magus can cast any spell forcelessly, without any added difficulty.

Thanks for your reply, but perhaps I have not made my problem clear enough.

According to the 4th ed. rules that I have, a fast-cast of appropriate tech+form succeeds if its level/casting total reaches half of the attacking spell's penetration. If everyone entering Dimicatio uses penetrations lowered to zero, what's the point of the contest? Any fast-cast would be strong enough against any threat, and the only challenge that remains is identifying the tech+form of the spell being cast to be able to select an appropriate fast-cast to counter...

Unfortunately I don't have Societates available to me, so its page 21 is of little use to me... However I suspect that there is a crucial bit of info in there that is obvious to the 5th ed guys but not to grumpy, backwards 4th ed resistants like me...

Another way to look at it is this:

'Forceless casting' simply causes a spell to not penetrate, if the target has any type of magic resistance whatsoever. Even a magus without parma still has minimal protection afforded by Arts, so... a spell cast forcelessly does nothing to them. It also has no effect on things with Might.

Counterspelling in 5th edition requires a spontaneous spell of half the level, not half the penetration, incidentally.

The easiest way to deal with it in 4th ed is probably just to go with 'forceless spells never penetrate', but still calculate penetration as normal for other effects that depend on your penetration total.

Ah, I believe that is the answer I needed. Fast cast to half the level... I could probably implement this in the context of Dimicatio.

Then, one last question: the Lion & Lily paragraph about Dimicatio states that by using forceless casting, there could still be an occasional dangerous mishap that makes the spell able to penetrate anyway... Is there any random element in 5th ed forceless casting? Or is it just 0 penetration, no die no nothing?

You're still casting spells in a stressful situation, so... you still have a chance of botch. So... it could be valid as a botch in those situations.

Some of it's also politics; it's convenient to have a chance to 'accidentally' pilum of fire some guy you don't get along with.

I understand... Looks like the implications of this concept could be funny. So any spectacular attack spell can be easily made into "just a frightening illusion" with forceless casting, as long as you know your target is a mage or is a creature with might...

I run a 4th ed. campaign for a couple of my stubborn players who see no need to move to 5th ed. (fools!!)

I have adapted the 5th ed. mastery rules to 4th ed. It's easily done, and then you can use the Dimicatio rules....


I wrote the dimicatio rules, and I can affirm that this thread is exactly correct in explaining the rules. I guess the Lion and the Lily didn't explain what "Forceless Casting" is, and that was the source of the confusion (not everyone has all the ArM5 supplements).

Just an aside here, that Fast Casting combined with Parma Magica (using 5th Edition Magic Resistance rules) can be very effective. Low level spells have high Penetration but are easy to stop with Fast Casting. High level spells have low Penetration and are easy to stop with Parma Magica. It isn't an official part of the background or anything, but in my saga this two-layered defense was one of the reasons House Diedne fought so well in the Schism War.

Again in my saga, House Flambeau adopted the Fast-Casting tactic, and the original purpose of dimicatio was as a training exercise to practice form of defense.