I am trying to understand what counts as a spirit for the purpose of 1) a major focus on spirits (that a Tytalus magus in my saga has) and 2) for the purposes of binding a spirit as a familiar. Which of the following would you count as a spirit?
b) Ghosts (and if bound as familiars, can they leave their haunt?)
c) Bjornaer anima inner heartbeasts
d) Spirit dream travelers
e) Hyperboreans using spirit travel
f) a "portion" of any living being (e.g. could you bind the "spirit" of an animal or plant as a familiar, or target the "spirit" of a person with a spirit-bashing spell?)
g) Angels in corporeal form?
h) Demons in corporeal form?
Well I would rule any insubstantial being that cannot form a body composed of matter.
as for your examples this means:
a) Elementals: NO, they can form bodys compsed of their matter
b) Ghosts: YES (and if bound as familiars, can they leave their haunt?) This could be done by original research aiming at altering the ghost.
c) Bjornaer anima inner heartbeasts: Not so sure, do they have bodies?
d) Spirit dream travelers. That is nice.. So probably YES, leaving her body behind in another place.
e) Hyperboreans using spirit travel Do not know
f) a "portion" of any living being (e.g. could you bind the "spirit" of an animal or plant as a familiar, or target the "spirit" of a person with a spirit-bashing spell?) NO, I do not think so.
g) Angels in corporeal form? NO, as they can compos e a body
h) Demons in corporeal form? NO, as they can compose a body
Just to make this clear: These are my 2 cent. This is the ruling I would give in my saga. You should do as it fits best in yours.
Well, I'm fairly sure there are canonical rulings on Angels and Demons. As for elementals, it's fiddly as there are both "Spirits of Elements" and "Elementals". The former are spirits, and the latter are animate matter. Some spirits can manifest and achieve physical bodies, of course, and the waters get muddier still.
As far as binding a spirit as a familiar, canonically this requires a mystery virtue, albeit an exoteric mystery. I'd suggest still requiring it take up a virtue slot, but allow a magus to start with it. It's just too subtle a modification in normal magic theory to really justify the mystery title and fuss - binding spirits is, after all, something magi can do, albeit badly.
"Spirits" is on of those words, like "ritual", that is used in different ways in various places in the books. I would say that your Major Magic Focus would work on all the "Spirits" of the Magic realm. Faeries, Angels, and Devils are all from different realms and are not, in my reading of a very fuzzy area, "Spirits". Rather, that is how mages describe them, for they share many traits with "Spirits".