Destroy a castle with a teacup

Okay I just reread the description of durations on page 112 particularly this bit about non-instant perdo effects.

Okay pretty cool effect right. But what happens when it's a Circle/Ring spell.

Lets say you cast a Circle/Ring Perdo Aquam spell using a premade ceramic ring. The rim of a mug should work or you could have something custom made if you insist. Any water that passes the rim of that mug will be destroyed. Now stick the mug in a nice gentle running stream wait a good long while and come back and retrieve your weapon of mass destruction.

Now the next time your involved in a siege just toss the cup over the castle wall. The cup breaks, the spell's duration expires and all that water reappears drowning the inhabitants of the castle.

Should that work probably not. But that seems to be how the magic functions and I can't think of anything in the RAW that specifically disallows it. The mundane logistics of doing it with a ceramic circle/mug would probably cause trouble but there are certainly better ways of handling that part.

I can think of a few fixes that stop that use but there are still a lot of ways of taking advantage of the effect pretty much no matter what you do some with cheese and some without.

Nothing ever reached the teacup, nothing destroyed ever reappears. PeCo wounds don't vanish overnight. Destroy is destroy.

Depends if you allow Ring/Circle spells to be mobile or not.
Even if allowed , moving the mug out of the water , breaks the effect , imo.
It does not become a container for invisible , massless water that you may then transport where you will.
Do the same spell , but with people , using Corpus & possibly Mentem with He/Te requisites.
Throw mug over castle wall , it breaks , instant army.
Great for field maneuvers and with Leap of Homecoming , better , faster transport.

Try tracing the circumference of a mug , moving no more than five feet per second. (60 inches per second)
A mug in my kitchen has a diameter of 3 & 6/16th inches. Circumference is 10.6 inches approx.
To trace 10.6 inches in .17 seconds , some kind of Dex roll would be called for.
Obviously , you can trace more slowly in this case.

While nothing in making magic items in Ring form suggests that you have to trace them ,
it seems a bit rorted if you don't have to , as you can then create very small or very large Ring/Circle devices ,
without having to worry about Concentration rolls either.

Yeah but that doesn't mean it's specifically disallowed by RAW Just that it's open to interpretation. In fact I would hazard to say many troupes allow mobile circles without even thinking about it. Even immobile, disappearing circles could have some amazing uses.

How about I just take the move less then five feet per second option and just take my time tracing the mug. Say three seconds. Actually that was pretty easy. :slight_smile:
Circles that can be traced in one round, that is they have a circumference less the 10 paces do not require a roll. The roll is so you can extend the casting time to account for circles that can't be drawn in one round. Ritual spells or ceremonially cast spells don't even require those rolls as you have plenty of time to trace all but the most ridiculously sized circles,

Not talking about magic items heck you can spont a lot of these suckers it's just nice to have ready made but mundane circles all set to cast the spell on. Personally I like the idea of circle spells cast into wands or staffs more utility that way. Or how about charged items like paint and chalk. Yes you should be able to enchant actual circles as well if you want to. Of course for them you could just make tracing them the device trigger.

Nope. A Perdo spell with a non-Momentary Duration destroys things during this duration not only while this duration lasts, and then it reappears. Perdo is real destruction, not temporary suppression or whisking away to another plane, to bring back at whim.
It is not a Bag of Holding from 'that other game'. IMHO and by my reading of the rules.

OTOH, using a Muto aquam spell to shrink an amount of water - say a large lake - into the volume of a barrel. And then tossing the barrel into the city, when the spell ends the water returns to normal volume and size. Splish splash.

Nice!!! Will point Jordi to this effect. Presteris might be interested in this for his (wannabe) battle against Termaneagh the Manx dragon


This is one of the places where the flaw Harmless Magic (HoH:MC 87) can be put to good use...

Alexander in Magi of Hermes uses this sort of effect in several of his spells, for his expedition supplies.

True, and I have to say that I really liked alexander; it has a much less "standard" feeling to him than most of our magi. I had not made the inference to use this kind of spells as a weapon, though :slight_smile:


You brought up the wrong quote, because that passage ends with :

However, looking at the spells in the rulebook, there are two ways to use durations:

  • affect anything that becomes a legal target for the duration of the spell, but only as long as they stay a legal target (Lungs of the Fish, p.122)
  • affect everything that is a legal target when the spell is cast, for the duration of the spell (Incantation of Putrid Wine, p.122)

The first, coupled with the fact that a momentary Perdo spell is permanent, gives you that example: any earth that falls into the pit for the duration of the spell is also destroyed. The second should allow you to create a temporary pit, but earth falling inside after the casting remains. It would work as a way to 'store' objects.

However, what you propose to do uses both together, and I cannot think of an example of a canon spell that does that. Besides, why should the destroyed water move with the cup ? I agree that when the spell ends it reappears (or at least that you can design the spell that way), but why should it be anywhere but where it was destroyed ?

I am also against allowing movable circle spells, but that is a gray area in the rules (besides, you could always use different duration/target to get the same effect, even if not as cheaply).

Ouch! totally missed that. You know my troupes have always played perdo the other way. In that, the Perdo'd things reapeared at the end of any duration longer than momentary.(Hold over from earlier editions maybe?) Of course if Perdo destroy's just a property of an object like a fires heat that does come back at the end of the duration, Because magic can not make permanent changes in somethings essential nature. So you could still get some interesting effects using that "limitation" creatively. Depending on what "properties" magic can effect you might still be able to get similar effects to what I initially proposed.

Even going with the straight book example you can still get truly terrifying effects how about this spell.

Howling Void Perdo Auram ) level 35,
R: Touch, D: Sun, T: Part
Upon casting this spell the all air within 50 yards of the Magus is destroyed. Furthermore the air that rushes in to fill the void is also destroyed. This creates a cyclone of hurricane force winds around the Void causing massive destruction in and around the area. The Magus of course is caught in the center of this and must not only have a way of surviving without air but must also contend with debris flung into the void by the winds.

(Base effect 15(5 would destroy still air but not the winds that follow), Touch +1, Sun+2, Pat +1)

In the medieval paradigm, would air would rush in to "fill the void"? Remember, in period "vaccum", and the propensity of gasses to move/expand to fill it, is probably not known. Is the notion of "air pressure" foreign to th period's mindset?

If this was proposed IMS, I would say that this simply creates an area empty of air. Air pushed by the winds into the area would be destroyed, but sorry, no cyclone. :wink:

In short: Wind is not moving air in the medieval paradigm (in my understanting). Wind is a force that pushes air around. Removing air from an area does not create wind, as surrounding aire does not rush in to fill the void.

There's a discussion of what makes wind and other airy phenomena in the "Meteorology" section on page 28 of Art & Academe.

I can't find, but seem to remember, something about how the medieval paradigm doesn't think of air as something that could be absent; rather suffocation-like PeAu spells make the air bad for breathing, rather than absent. Can anyone figure out whether I'm remembering this right?

Well, the Romans used suction, so its functional use had reached Europe.

From what I can tell quickly, there was a lot of debate about suction, vacuums, and the speed at which air would fill a space at the time. The church was against the idea of a vacuum. In 1277 the church tried to firmly stamp out the discussion. So this discussion must have really picked up in roughly the Ars Magica time period.


Medieval people absolutely understood that air rushes in to fill a void. Horror Vacui the idea that nature abhors a vacuum was an important part of natural philosophy at the time, and was first proposed by Aristotle centuries before. This isn't surpising. The property of gases to rush in and fill an empty space is observable by anyone with an airtight container like a bottle. If you take and put a bottle to your lips you can suck the air out of it. If you work at you can get to the point were you might even think (unless you knew better) that you had gotten all the air out of it. If you then break the seal your lips make you will not only hear but probably feel the air rush in.

Edit again for clarity: Edit: Many people felt a true vacuum was impossible and that air would always move in fast enough to fill a void. The church apposed the idea of a complete vacuum as well because it suggested there might be someplace god didn't exist. If anything creating an area where no air exists at all is further away from the medieval paradigm then air rushing in to fill the void. you really wanted to make the aforementioned spell ascribe completely to medieval physics then the air couldn't be destroyed faster then the the winds could fill it. The destructive power of the spell wouldn't change (or it might actually go up) but the Mage at the center would need some major hoodoo to survive the duration. (or a fast cast leap of homecoming)

Aristotelean physics is weird once you start to think about it.

Now lets take all the rules at face value and say that yes the Howling Void spell is possible as written. That yes you can destroy still air as per PeAu level 4 and yes with a duration added on it will continue to destroy any air that enters the area of effect. This creates a perpetual hole in the air that persists until the spell expires or it's filled by something other then air.

Lets also say that as per Aristotelean physics air rushes in as fast a possible to fill it because of Horror Vacui (nature abhors a vacuum). Now here is the scary part remember how there isn't any inertia in the medieval paradigm anything that shows persistence of motion like an arrow is actually being moved along by the air around it. That's essentially Horror Vacui at work. Moving objects thin the air out behind them and the air rushing to fill the area the object is leaving is so forceful it continues to push the object forward. Air is turbulent so it does this imperfectly and an object will eventually slow down to it's natural resting state.

That means these winds are literally moving as fast as possible (hurricane speeds at least) with seemingly infinite force. These winds would pick up and carry anything not nailed down and 99% of the things that are. But any debris carried along by the winds is going to stop and drop just inside the area of effect no matter how fast it was moving because there would be no air to push it further. You would end up with a quickly growing pile of debris being pushed towards the center as more and more debris enters behind it. I can only imagine this looking like some giant tidal wave pushing inward.

The mage who casts the spell as written would probably be crushed in moments and the void would be well and truly filled soon after. Still if you let it past effects like this spell would be the mother of all magic resistance killers. MOAMRK