It is a bit more complex than just referring to page 82. And people did refer to that page, and people have also referred to page 112, as well, so perhaps you need to do a bit more reading yourself?
What constitutes breaking the ring? Physically breaking it? Crossing it before the spell is cast? Laying something across it to interrupt the magical energies? None of that is mentioned.
I'll also note that you've not added anything constructive to the discussion and just blathered annoyance... Blather, indeed!
Yes, it seems tricky/dangerous to practice MuVi effects. I'm not sure that is a problem, it's just a consequence of the rules, a fact of the gameworld that (in-character) anybody with Magic Theory knows. I guess it means that books on MuVi spell mastery are therefore both rare and valuable.
Alternatively, you can resolve the problem by saying that "practicing" a spell does not necessarily imply "detonating" the spell. You can just go through the motions, without actually casting it. In much the same way that many people say this is true of "practicing" rituals --- i.e. you can "practice" a ritual without expending lots of vis.
I'm not sure that there is a point of disagreement here.
The RAW seems to say, for ring casting:
If the ring is large make the required number of Concentration rolls, and a Casting roll.
If the Casting roll fails, the spell fails.
If the Casting roll botches, the spell botches.
If the ring is broken during casting, the spell botches.
If any Concentration roll is failed, the spell fails, and if the Casting roll was a Stress die, check for a botch on the Casting roll. If the Casting roll was not a Stress die, then the spell does not botch (due to failing the Concentration roll).
If any Concentration roll botches, then the troupe decides the effect of this. As it is a Concentration roll to maintain concentration on casting a spell, it is likely to be a similar effect to botching the spell itself, which doesn't necessarily mean the spell fails, it just means something unexpected happens. But there are any number of non-spell things the caster could do wrong, from swallowing his tongue, falling off a cliff, stabbing himself in the foot with his dagger talisman, walking into the grog with the loaded crossbow, etc. Depends on the particular circumstances, and what the troupe decides is plausible/fun.
Lets see... in 2 posts, 4 lines I've mentioned chalk breaking the circle, warping and p82 which clearly states failing a Concentration requires checking for a magical botch. I think that's a fairly good S/N ratio.
Why can't we take a step back, do some research to summarize the issues and resume from there instead of the runaway train that "breaking a foot-thick marble ring is impossible" has become?
It does not state that. It states that failing a concentration check requires a roll to check for botch if the die was a stress die. Since this magi presumably isn't casting this spell under undue stress no checking for magical botch. Secondly why would chalk break any well made circle? Putting chalk across my arm, does NOT break my arm.
Tugdual, Lamech is right. The concentration botch does not create the circumstance of a spell botch, or even a botch check. I think it should, sometimes, but it's not explicitly stated so in RAW. Of course, this is why I suggested rereading the pages indicated, because they do not say what you think they say.
So, perhaps you noted that I had earlier said that failing wasn't actually easy to do.
With an Int of 3 and 15 experience points in Concentration (spells) my Concentration checks will never fail unless I botch, which is only 1 in a 100. A botch only changes the total to 0. A 0 rolled without any botches doesn't add anything to the total, but you only need to get to a EF of 6, which is already done in Characteristics and Ability scores.
So, there is some contradiction in RAW, with the line that big circles are rarely worth the risk. As far as I can tell, unless a concentration botch means that a spell will also sometimes have to check for botch (presumes the roll was a zero and botch dice for the spell casting are rolled) there really is no risk for large circle spells. The point I have been leaving unstated, up to now is that the rules are at best unclear, or don't work as intended, if we can rely upon the statement: "[r]eally large rings are unlikely to be worth the risk." I do like the idea that if you botch the concentration roll that the spell casting die must become a stress die, that does introduce the element of risk into a circumstance where I see none explicitly laid out in the rules, and it is close to RAW, because if the concentration roll were to normally fail, and the casting were using a stress die, you add an extra botch die in the event the casting roll is a zero.
Ah, ok. The only way to fail the p112 Concentration roll is to botch, because almost all magi have Int+Concentration = 6. Now I see the shortcut, sorry.
So you have about 1% failure rate on the Concentration roll, which is an automatic fail on the spell casting. If the spell was stressed, you roll for botch with an extra botch dice as you say.
I also believe extending the ring makes it stressed, which would yield a 0.2% chance of getting 1 Warping point. A 60 paces circle (5 Concentration rolls) has 6% chance of botch check and 2% total chance of botch. Compare to the 1% spellcast only if you can extend without stressing.
Of course, you have 50% chance of having to restart a 700 paces circle just on Concentration botches alone, so you have to be patient when covering more than 100m radius.
No, the only RAW "not worth the risk" is enemy action or any sympathetic effect that can symbolically break the ring.
