When it comes to realms and supernatural powers, I have been finding myself confused more than once.
So I want to try this thread to fix once for all this matter.
Rules are taken from ArM5 core rule book, p183.
First: the power are affilied like this:
for virtues and non hermetic arts, the realm with which the player or the SG affiliates them. Generally magic,
For infernalists, infernal; divine for most priests and divine powers...
Hermetic magic is generally magical, but:
chthonic magic affiliate you with the infernal too (ROPI)
holy magic affiliate you with the divine (ROPD)
faerie magic with the faerie (ArM5 p183)
Homoculous magic affiliates only with the faerie realm IIRC. Second, consult the table (ArM5 p183) for the value. and apply the better adjustment.
-> magical and divine affiliated magic (holy magic for example): add magical or divine aura, add half faerie; no penalty from infernal.
-> magical and faerie affiliated magic (merinita magic): add magical and faerie, substract infernal and 3x divine
-> magical and infernal affiliated magic (chthonic): add magical and infernal, add half faerie, -3x divine
ROPtI is confusing: (page 12, c 3, first bullet and last paragraph before "magical reactions to the infernal"): "Note that all humans - even those affiliated to the Infernal realm - suffer these effects". Does that mean that supernatural entities and animals don't suffer extra botche dice/penlaty?
Third, in case of botch, the aura may add a certain number of those. This part is REALLY unclear.
no botch dice from your alignment aura.
ArM5 p183 shows an example: "if (a magus who has also a faerie based power (not faerie magic!)) moves to a forest with a faerie aura of four: he adds two to his hermetic total but adds 4 botch dice.
"The divine is not hampered by auras of other kinds" : does that only worth for step 2 (penalty or bonus to casting total) or for step 2 and step 3 (botch dice addition?)
If I try to do a table, your character will use the least additional botch dice from all his affiliated realm related to the current aura:
[table][tr][th][/th][th]Magic aura[/th][th]Divine Aura[/th][th]Faerie aura[/th][th]Infernal aura[/th][/tr]
[tr][td]Magical power[/td][td]+0 dice botch [why not -aura value??][/td][td]+ aura dice botch[/td][td]+ aura dice botch[/td][td]+ aura dice botch[/td][/tr]
[tr][td]Divine power[/td][td]no botch dice[/td][td]no dice botch [why not -aura value??][/td][td]no botch dice[/td][td]no botch dice[/td][/tr]
[tr][td]Faerie power[/td][td]+ aura dice botch[/td][td]+ aura dice botch[/td][td]nodice botch [why not -aura value??][/td][td]+ aura dice botch[/td][/tr]
[tr][td]infernal power[/td][td]+ aura dice botch[/td][td]+ aura dice botch[/td][td]+ aura dice botch[/td][td]no dice botch [why not -aura value??][/td][/tr][/table]
Looks correct to me. As for the "why not - aura botch dice", why should there be ? Using a power in the aura it is affiliated to uses the normal botch dice for that power, that seems simple enough. Having more power available does not make it any less dangerous if you screw up enough to botch...
The point that is not entirely clear is the one regarding Divine powers, non-divine auras, and botch dice. I, like you, read the rules, notably the "The Divine is not hampered by auras of other kinds" and the fact it is left out of the examples, to mean that it has neither casting penalty nor extra botch dice, no matter the aura.
Another which is unclear: when a magus affiliated to 2 (or more!) realms invent a spell or cast such spell : is the spell affiliated to only one, or always all his affiliated realms?
Each power is affiliated to a realm, and only one: Hermetic magic is affiliated to the Magic Realm (or the Faerie realm for Merinita), Holy Magic to the Divine Realm, and so forth, regardless of the magus' other affiliations. If a Holy Magus casts a Hermetic spell (not a holy spell) in a Divine Aura, for instance, he suffers the casting penalty and extra botch dice for using a Magic Power in a Divine Aura).
But it's not described as it. See Chthonic magic (ROPtI123), for example:
"the chthonic magus becomes attuned to both magical and infernal auras, and so gains warping points from neither, and the benefits of both"
here, it's the "magus", not his magic, which is attuned.
same for "holy magic" (ROPD p69): "holy magic is attuned to both the divine and magic realms (...) magi are still associated with the magic realm because of their gift(...).
I always thought that both apply, and since both use hermetic magic as a basic, even if doing maleficia or miraculous effect. But your answer shows that it's not as clear as i thought.
The realm interaction table is explicitly about powers, and the example p.183 of a magus with various powers attuned to various realms, is quite clear: each power is considered individually.
Gaining warping points from auras is a different problem, and there a character benefits from all his mystical abilities: a Merinita gains warping points from neither Magic nor Faerie auras, a Holy Magus is safe in Magic and Divine ones, and so forth.
the example in the core rule book gives a magus with hermetic magic (magical attuned) and a faerie power (faerie attuned). It don't give the example of a magus attuned to both realm (as would be a holy magus, chthnoic one or even a magus with faerie magic virtue).
holy magic says, in the same sentence: "holy magic is attuned to both the divine and magic realm. This means the magi receive no penalties in Infernal auras, and may add the level of the aura to their spells in magic and divine places".
So, if I try to integrate all datas:
Only one realm affiliation for power and virtues;
however for "magic", we should look at the magus type of magic. There may be in some case multiple realm affilition for his magic activities (obvious are chthonic, holy and faerie).
the affiliation of a character to a realm (by "touched by realm", or his "gift" or "methods and powers" or even "ars fabulosa") make him unaffected by warping from that aura.
In some case, that could be from multiple auras (chthonic magic, faerie magic, holy magic).
Most characters with "basic" powers (for example second sight or entrancement, or even sense holiness and unholiness) are not attuned to a realm : being attuned to a realm needs a special comment in the virtue to be effective (see "touched by realm" (C&G p71) which has that explicit comment) and it is not sufficient to have a power affiliated to a realm to make the character affiliated to the realm.
To align spells to a realm, see the Minor Breakthrough Realm-Aligned Spells (HoH:TL p 34). It can negate all botch dice if your (Realm) Lore is high enough, whether they came from the foreign aura or not.