We are getting further and further away from the original question, yet I will give by 2 c.
Regarding any sacrifice, magic-users relying (frequently) on it to power their spells should be mindful of the Code saying "I should not bring harm to my sodales". To my understanding, dealing with demons was forbidden initially on the ground on moral or religious reason but because it would cause sooner or later trouble. Whether it would be attracting the Church's attention or because demons will simply cause trouble.
By the same token, I believe reading in RoP: Infernal that Ablating demon is not so well considered by Quaesitores, because even if it destroys the demon, recurring usages has a chance to attract Hell's attention who might decide to take action against this gang of wizards who like to leach demon's power.
So sacrificing a chicken from time to time bear probably no consequences, however sacrifice a great stag might anger forest spirit, genius loci and what not. There are no specific rules preventing it, but it is another story seed for a ST: quaesitor advising to refrain from such practice (whether there are legitimate concerns or it is simply a political manoeuveur by a rival mage is entirely up to the story), spirit putting a geas on the practitioneer or simply going vengeful berserk ("You killed my favorite hen!").
Finally, it is possible that practicing regularly sacrifice in the same spot might create an aura, or taint it - more story element.
Hm. Well, assuming sacrifice would actually work, I would imagine that it would be used in conjunction with Form of X, rather than by itself, as the minimum level to create an Elemental is something like 25 or so. Assuming you could use a form of sacrifice in this context, you'd need that Stag in order to get things done. Or without it, knock yourself out for a week (ie, spending 5 or 6 levels of long-term fatigue) in trying to cast the spell. In contrast, a "sheep without blemish" probably would provide 3 pawns of vis, but has the advantage that you can buy a few dozen using the Summon Hermetic Petty Cash spell. Plus, you're probably not going to cheese any local spirits off in doing so.
But this gets into the whole issue of summoning an elemental (which doesn't require vis, as they're like airy spirits in that they inhabit the mortal realm), to creating one (which does require vis.)
Unfortunately, to argue against my own point - summoning is different than creating. And Hermetic Sacrifice is all about summoning pagan spirits, whereas you point here seems to be (mostly) about CREATING elementals, using the rarified guidelines from RoP:M, pg. 133. Now, personally, I would allow the Hermetic Sacrifice, but I'm pretty easy to amuse in that sort of way - and based on personal gaming experience, vanilla Hermetic spirit magic isn't all that great (well, Vim-base Realm wards are pretty good, and PeVi Might Strippers are probably overpowered. And if you want to delve into Hermetic Spirit magic, Invoke the Spirit of TeFo is probably overpowered enough to be restricted, at least the MuVi version.). However, a reasonable reading of the Hermetic Sacrifice rules probably wouldn't allow it. Thus, this would have to be a troupe/GM decision to OK it.
However, I'd argue that it should be a relatively easy thing to get changed, for the abovementioned "normally spirit magic kinda sucks, and needs all the help it can get." However, caveat emptor, and all that. (And I think I've mentioned this, but one way that would make Elementalism not suck if it could use all the integrations from Elementalism in Hedge Magic - which includes the ability to cast Elemental spirit magic without needing penetration....at least after the first casting.)
By sacrificing an animal of the correct humour, you release energies appropriate to shifting the balance of elements in the surrounding area favourable to the appearance of entities associated with the element - ie sacrifice a choleric animal for earth elementals, aquatic or cold blood creatures for water, birds for air, etc. (Certainly works in a similar way for Amazon sorceresses who power their rituals with the vis from magic animals)
If you are creating an Elemental, can you create it with a Personality Trait of Loyal +3 and have it loyal to you rather than using a lot of Rego to keep it under control?
If Minor, have it only be the Elemental magical things. If Major, It would expand to any supernatural thing aligned to Ignem, Aquam, Auram, or idk uhhhhhhhhhhhhhhhhhhhhhh terram.
didnt meanto reply to tellus btw sorry
Altering the base creature in such a specific and meaningful way should be considered an additional effect...so an extra magnitude on the creation spell.
