So I'm making a new character after a spell mishap involving about a thousand tons of rock. It's a Merinita who will be of the Line of Quendalon. According to the book, many of Quendalon's line possess a Major Magical Focus with Faerie. What exactly would this do? Does it affect the following:
Spells cast with faerie magic ranges, durations, or targets
Spells invented using the Faerie-Raised Magic virtue
Spells designed for use on/against Faeries
Animae Magic (which creates faeries or brings out faerie qualities)
I would definitely say yes to 3) and 4) since the spell would indeed affect faerie things. As for 1) and 2), I would say no: the examples are just improvements that sympathy with faerie provided to vanilla Hermetic magic. Note that other Infernal and Neo-Mercurian mystery virtues provide very similar ranges ro Road, and that if look closely at the Faerie-Raised Magic virtue description, you will realize that despite the name, one does not strictly need a faerie background to have it, it's just the most common occurrence. The magus might just be exceptionally flexible and creative at making up spells because of vanilla talent, just like all the other oddball hermetic virtues.
I was thinking that it would boost spells and lab activities that affect faeries and faerie things. As Wanderer suggests, 3 and 4 are obviously appropriate. 1 and 2 are probably out. It's not a focus with Faerie Magic, just faeries-- though perhaps that's a variant Major Virtue worth considering. I'd imagine that a Faerie Magic focus would affect 1 and 4, but not necessarily 2 or 3. That might be too broad, though, because you could argue that any spell cast in a faerie aura is a Faerie Magic spell.