It has been suggested that it would be useful to have a summary of all the standard sources of botch dice near the Dangers of Spellcasting section.
The obvious ones are:
Foreign aura: +1 die per level, double in regiones
Vis use: +1 die per pawn
Fast Casting: +2 dice
Spell Mastery: -1 die per level
Virtues and Flaws are not appropriate here; if your character has them, you know what they do, and if your character doesn't, they are irrelevant. Are there any other general sources that should be noted?
One thing, I find unclear. Should there be extra botch dice for extra-ordinarily stressful situations like combat?
I would take a bit care with the word «foreign». It applies to auras of a foreign realm, but is easily misread for an unfamiliar location. I agree that it is hard to find a good wording for a table format.
If you're doing this, I would include notes about when you're casting stress-free. First, that there are no botch dice at all. Second, that there are still no botch dice if mastered, but you roll a stress die anyway. Third, there have always been questions about safely casting mastered Rituals since you satisfy the Ritual rule by using the stress die from mastery, meaning there is no clear statement about whether all those extra botch dice from vis use can just disappear.
Edit: While I know you don't want to include Virtues, this is probably the place for me to point out that there remains the eternal question of whether Cautious with Artes Liberales / Philosophiae apply here.
Does Quiet, No Words, and/or No gestures, give no extra both dice?
A -15 penalty seems like it should give serious bonus botch dice, however, it seems it does not.
Someone reading the rules may assume the extra botch dice comment is hidden somewhere and go searching. Explicitly stating there are no extra botch dice in the "words and gestures" paragraphs on P83 of the core rules would be useful.
For what's it's worth, I think if someone is trying to cast a spell with no words and gestures they should get extra botch dice, however, that's probably for a different thread.
I do not think that they would be "useless Virtues". For example, cautious with Artes Liberales is great in debates, when attempting ligatures, when computing horoscopes, and in many other circumstances too. Of course, it is mostly helpful to someone who focuses on Artes Liberales, which is not true for most magi.
On the other hand, allowing either of these two minor Virtues to remove the last botch die from any magic cast ceremonially in addition to their other benefits seems unbalanced to me (it would not if the last botch dice remained "uncancellable" as in Cautious Sorcerer).
Well ... rolls for combat abilities used in combat are stress, while it seems reasonable that if you rolled your combat ability outside combat just to show how good you are at it it would be a simple roll. So, in some sense, rolls for combat abilities do get extra botch dice (moving from simple to stress rolls) for being used in combat! Which is what happens with formulaic spells too.
However, fatiguing spontaneous spellcasting is stress even in otherwise calm conditions; it makes sense to me that if cast in the middle of combat it might involve extra botch dice. In some ways, this is already captured by Concentration rules (if the caster is himself in the middle of combat) or by Fast Casting rules (if timing is critical). But I daresay that casting a spontaneous Pilum of Fire on an enemy locked in combat with an ally would entail an extra botch die.
When casting a spell under stress, you start with one botch die, as normal. The storyguide can increase this for all the normal reasons, such as distractions or a difficult magical environment, but there are several standard modifiers to the number of botch dice for spell casting.
Using vis while casting: +1 botch die per pawn of vis used
Casting in a supernatural aura other than Magic: +1 botch die per level of the aura, doubled if in a regio
Fast Casting: +2 botch dice
Golden Cord to a familiar: –1 botch die per level
Spell Mastery: –1 botch die per level
Note that there are a number of Virtues and Flaws that can modify both the number of botch dice, and what they mean. For example, the Faerie Magic Virtue attunes Merinita magi to Faerie auras, so that they do not gain additional botch dice in them.
If the maga is relaxed while casting the spell, then there are no botch dice, no matter how many the circumstances would normally add. Note that it is not possible to be relaxed while casting a Ritual spell or a fatiguing Spontaneous spell, as the process itself is stressful.
You are probably right that it does not belong to the present question, but I really do miss some guidelines and example for extra botch dice, not just for spell casting. I find myself basing the number on the question, how much narrative fun can we make out of a multi-botch in this situation?
I kept the post short. I had a rambling part about cautious sorcery, flawless magic and spell mastery being so critical in a combat heavy scenario they become nearly obligatory, which isn't great.
Thus my thinking a mage behind a wall of grogs with only melee combatants could be considered relaxed. Live and learn.
Oh, so, wait: you always get a whole lot of botch dice when (re)casting an Aegis or other Ritual, even if it's a "routine" casting?
For some reason, I was convinced that the current interpretation was that Mastery 1 allowed you to avoid all botch dice in an otherwise relaxed environment. Falke won't last long recasting that 12th magnitude Ritual to call the spring every year...