In an effort to be helpful (and provide one of the things that I said the core rule book needed) here is a list of all the things (or at least all the things I can find) which can affect a spell roll’s number of botch dice.
NON-MAGICAL AURAS.
+1 die for each level of Fairy, Divine or Infernal aura. This is doubled if you are Susceptible to that Power.
REGIONES
If you are in a non-magical regio then double the number of botch dice.
VIRTUES
Cautious Sorcerer (-3 botch dice to a minimum of 1)
Diedne Magic (Eliminates botches on some spontaneous magic)
FLAWS
Careless Sorcerer (+2 botch dice)
Susceptible to (Realm) Power: See above.
Twilight Prone: Makes you check for Twilight on just one Warping Point instead of two.
Weird Magic (Special. Adds an extra but separate botch die.
RAW VIS:
+1 die for each pawn of raw vis used whether to enhance a spell roll or to power a ritual spell.
SPELL MASTERY:
Your level of spell mastery reduces the botch dice by its level. This may reduce the botch dice to zero.
BROKEN CONCENRATION:
If you are physically distracted while casting a spell and then fail the concentration roll needed you then add a botch die.
The general botch die rule from page 7- Anything that makes an action more difficult gives the character an extra botch die - should, I believe be included in the list.
I've edited the top post to include the matter of Regiones. It say in the book that botch dice are doubled in a Regio. Do you think it means just the botch dice due to aura or all botch dice?
I think it is the general case and the broken concentration rule is a specific application of it.
The general rule would covers things like being drunk, being on a moving ship, being harassed by a flock of parakeets, having ants in your pants, suffering from the flu, needing to pee badly, having your vision obscured by two black eyes, being extremely sleepy, having just been hit on by a nymph, having sharp rocks in your shoes, having magically induced hiccups, casting while balancing on a swaying rope ladder, extraordinary strong winds, being soaked with gravy, casting in an exceptionally smoky room, having your legs in a splint, having your hair smoldering, being naked, bashful and observed by others, having your familiar screaming at you, having annoyed the story guide by quoting too much princess bride, being very cold, being very warm, having just been branded, being under the effects of a rego mentem spell that makes you unable to say the word "creo", suffering from a plethora of insect bites, having a difficult time controlling your laughter, being overwhelmed with melancholy, being tickled by a three year old, casting a spell on someone who looks like your true love, being shape-changed into a rhinoceros, being in free fall, casting as a nearby volcano is erupting , casting while overwhelmed by the stench of 30 corpses, or any other reason.
Golden Cord of familiars may reduce the number of botch dice down to 1
Faerie Magic, Chthonic Magic, and Holy Magic make hermetic magic fully aligned with the respective realm, just like the spell was a power of that realm, which removes the extra botch dice, it is like the magus was casting in a magic aura.
There' s probably more, but that's what I can think on the moment, without taking a full skimming of the books
