Rather than derail the thread where this came up...
The question arose whether a Hermetic Spell could remove (short term or long) Magic Resistance that was not based on another Hermetic Spell, specifically with regard to this discussion, Magic Resistance that sprung from a creature's Might.
Note- There is much here that is left unanswered/unexplained by the RAW, and so much that has to be assumed/interpreted by each SG/Troupe - there may not be a single "correct" answer in canon, so this may be a more "philosophical exchange" than a definitive citation of RAW.
Actually, there is no such mention under DEO, the description of which is quoted in its entirety below:PeVi
"Weakens and possibly destroys a demon. If the spell penetrates the Demon's Magic Resistance, the demon loses Magical Score* equal to the spell's level." (p. 160) (* Note- Technically. an Infernal demon has a "Might Score" or an "Infernal Score", but not a "Magical Score", since it is not a creature of the Magical Realm. What the differences are between (X) Might, Might Score, and Might Pool, and how they interact, require some closer reading...)Creature Might
"[i]Magical Creatures have one of (the 4 Mights), depending on the Realm to which they are affiliated. Might Score... provides Magical Resistance, fuels the creature's powers (& etc.) The higher the Might Score, the more powerful the creature.
...A creature that hasn't used any powers recently has a Might Pool equal to the Might Score. To use a power, it spends the appropriate number of points from the Might Pool...
Might Pools... refresh to the creature's Might Score over the course of a day (unless otherwise noted...)"[/i](p. 191)So, if I read this right - X Might is the max, Might Score is the (current) max, Might Pool reflects powers used*.
(* The question whether a Pool is reduced by the amount a Score is reduced, or whether merely the maximum is reduced, remains undefined. That is, a creature has a Score of 20, but a current Pool of only 10; if the Score is then somehow reduced by 5, how much is now in the Pool?)
To me, Infernal Creatures work differently than Magical Creatures that are native to this "earthly plane". A Demon, imo, can be banished because it is not a creature of this "plane", but of the infernal regions - once its Score is reduced to 0, the magic holding it here is broken. However, a unicorn or dragon is an earthly creature, and that feels markedly different to me - it is not tied here by its magic. However, altho' not specifically addressing other realms, that does open the door to the discussion of reducing any Might Score of any creature (except the Divine? A different discussion, please...)
I think it is clear that while Demons can be banished, Magical/Faerie creatures would not be so effected. The difference is the corporal aspect of their existence- a Magical ghost would be destroyed, but a Magical Unicorn would still be a horse with a horn, etc.
I was always under the impression that Hermetic Magic could not directly attack an animals' Magical Resistance, that it was part of its "essential nature". The idea of a Mage reducing or removing, say, a dragon's MR with a spell just seems a bit off, and it was Penetration that was required for any spell against a given Creature with Might. A Magical Might 50 dragon is, and always will be, MM 50. MR will stay the same, even if the Pool to use it's powers is depleted.
Also, if one were able to "weaken" a Magical creature, then a smaller Ward against Magical Creatures would be effective than against stopping the identical creature that it could not before it was weakened- and that doesn't seem quite right either.
It's clear that different Realms can/do work differently, and interact differently with Hermetic Magic. The Divine enjoys advantages over Hermetic Magic- perhaps the Infernal suffers penalties that Magical/Faerie creatures do not.
However, I can't find anything BTR that supports one interpretation or the other definitively. Perhaps it's just a matter of personal paradigm, or perhaps I'm overlooking something (not for the first time!) - I'll throw the door open to others, for their opinions, personal interpretations, or (always best!) citations.