One of my players asked how to create a certain spell and I confess I'm stumped. What she wants is a simple alarm spell, along the lines of "when X enters the area Y event Z happens (or stops happening)."
Using Hermetic magic (core rules only) how would you do that?
Rego Vim: Watching ward for a one time trigger
Enchant a magic item with some sort of Intellego trigger.
Intellego Corpus, with Creo & Imaginem as requisites (presuming you want to detect human intruders that is)
Yeah, I think that's what she was thinking of. Thanks!
Sigh. Except that that will not work as a spell, not without a ~very~ creative interpretation of the rules. As an item, yes - but to cast the spell, it would only grant the caster the ability to detect the bodies - and then what point is there in the alarm?
Intellego allows the caster to supernaturally sense a target, or to change their own (or another's) senses, yes. The CreoImaginem will create a sound at the Caster's will, certainly. But the two will not linger in place without the Watching Ward - which is exactly what that is intended to do.
What your player wants is to create a small, temporary magical enchantment, to perform a task long after they are gone. Unfortunately, Hermetic magic does not create "land mines" in such a way, to linger and wait, not without vis, or stepping far outside the RAW.
Such a spell share some of the same fallacies as a "pseudo-ward" - is the Range to where the spell lingers, or from there to the detected target, or from the lingering spell to where the mage wanders after casting? Is the Duration the time the spell will linger, or the time the alarm will sound? It simply doesn't fit the Hermetic parameters, unfortunately.
As a magical item (or with a Watching Ward), such a trigger and connected effect can certainly be created and tied together, no problem. But short of that... not so much, no.
Take the guideline of InHe "shriek of the impending shaft" This spell makes you realize any incoming wooden objects.
So if you want to set of the alarm whenever a human is near it will be InCo, InMe to warn you of any murderous thoughts nearby, InVi to tell you whether there are any creatures with might... and so on. Magintudes may vary depending on the form related guidelines.
Unfortunately I do not remember which book contained the "shriek of the impending shaft". Serf’s parma!
Shriek is in the core book
Cheers,
Xavi
I would also like to point out that the only thing that makes Watching Ward a Ritual is it's potentially indefinite duration. It is the only vanilla spell that can last for years or decades or longer. A Watching Ward that had a lesser duration, say Moon, would not have to be a ritual. Just use the ReVi guidelines for "creating a spell container"
A Watching Ward is a ritual not just because of its potential duration, but because it changes the rules and potential of any formulaic spell beyond normal Hermetic possibilities. There is no way otherwise that a formulaic spell effect can leave, say, a fireball behind as a "land mine" (the best analogy I can think of), no way to design it that way*. Watching Ward creates a trigger, as if the spell were not cast until that moment, and regardless of the location or condition of the Caster or casting modifiers. That is the reason, as much or more than mere Duration.
(* I think an effect could be ~timed~, but not triggered.)
Yes, but this is not that.
A personal Intellego Form spell alerts the Caster* (the "shriek" is a perceived effect, not one heard by any and all around), and the effect of the spell is to change/augment the Caster's senses.
(* Or the "Target", the one whose senses have been magically attuned to the Form in question.)
Lucius' player, from what I understand, wants to be able to drop this effect behind them somewhere, and the CrIm "noise" then alerts all who are around at that time - no longer tied to the Caster's senses in the least.
(Or, to build it the other way, they want to create a noise, CreoImagonem, but not have it activate until the InCo spell detects the desired target - and again, we are outside Hermetic bounds for a formulaic spell effect. InCo does not change "the senses" of a formulaic spell - tho' it can be used to create an appropriate trigger if constructed as "linked" in an Invested Device.)
The distinction is an important one, and hardly a fine line - and exactly what makes AM magic different from (and imo preferable to) some other games where magic does "stuff" without any real considerations for how.
(If the spell is centered on the Caster herself, and not "left behind", but merely acts to call the alarm rather than rely on the maga to do so, that solves half the problem, but not all of it.)
Of course, SG's and Troupes can do as they please, to tell the story or achieve the effects they want - but they should be clearly conscious of the fact when they're coloring outside the lines, so later effects inspired by that ruling are recognized as being based off of their "creativity", and not anything in canon. 
As usual, I respectively disagree. The base Parameter, "form a spell containter", does not indicate at all that a Ritual is needed for the effect. It is the Indefinate Duration, and only this Duration, that requires the spell to be a ritual. It does nothing beyond Hermetic Limits, because the ability to make spell container is indeed part and parcel of Hermetic Magic as described using Rego Vim.
The best idea for this though is a charged magic item with environmental trigger Built into the effect.
If you want it permanently triggering then a lesser magic item with environmental trigger or regular magic item with in trigger effect built in.
Watching ward type effect is good for a one time delay.
I'm with Marko here the guideline is in the book with no reference to requiring a ritual. I don't think that it makes sense to infer that one is necessary.
I also think that spell containers are fantastically cool and lots of fun. Lighten up sourpuss, let your players enjoy themselves 
(that was meant in good fun, not as an accusation of cold hearted sourpuss-ness)
I sourpuss flamable? Goes and tries to cast some CrIg on some sourpuss people to test it. easy to find at work
Cheers,
Xavi
Actually, I've (intentionally) made absolutely no comment on how "I" would rule on this.
(Mainly because, without knowing the Players, the Troupe, the Saga, it would be less than meaningless.)
I just have a kneejerk when someone waltzes up and says "Oh, it would work fine like this...!", implying (or actually claiming) that that's how the Rules read - when it's blatantly not.
There are many, MANY parts of the rules that have been left open to interpretation - and this is arguably one. But what's important (imo) is that ~that~ is recognized, that's it's interpretation - and as such, there is no single "right" or "wrong".
The difference is why some readers/posters make a statement or have an interpretation or question that seems completely out of left field, and then when "The RAW" are presented, they seem completely boggled as to how their (mis-)understanding ever came about in the first place.
It's because some posters present their "interpretations" as Rules clarifications/explanations, and/or claim their opinion is universally and objectively "correct", when in fact they're just one poster's opinion, perhaps based on nothing more than what mood they were in on that day and a patchwork reconstruction of some long-ago forgotten rule in one edition or another. As if they were on a one-man crusade to misrepresent the Rules on these boards, and replace them with their own creativity and random guesswork. 
I often do the same thing - but I always try to make that clear when I do. Some don't. That's what sours my puss, not the ruling itself.
But that is how the rules read. I always quote the exact rules. Other people like to get into detailed metaphysics and philosophical theory that are not part of the game, and use these to make the claim that there is secret RAW written between the lines.
Always? Really. Like the (complete lack of) rules you "quoted" above?
Why don't you quote where it says one spell effect can work as a trigger for another in a formulaic spell - which is required for the spell you blithely offered.
We'll wait right here. (But I won't hold my breath.) 
someone already did it for me 
Rego Vim guidelines:
"create a conduit or container for spells with level less than the level +5 magnitudes of the Vim spell. A conduit puts you in mystical contact while a target (effect Touch range), while a container will hold a spell before a specific length of time before releasing it."
Quite clearly, possible to have a temporary, non-ritual watching ward 
I had never thought about it, but it seems like a good alternative.... if you do not mind having to replace all your watching wards once per month or so.
Cheers,
Xavi
RIght, you can make a non-ritual, shorter duration watching ward and if high enough level, it can hold two spells of which one can be a complex In spell to test for condition to trigger the second.
Exactly