Yes, rituals must be 20th level, but I can't find where that is explicitly stated right now. Since the Aegis is a ritual, yes, the lowest Aegis is 20th level, and there's no advantage to lower the base effect to make it as a 10th level spell.
Your question begs the quest, why don't they have a lab text for Aegis of the Hearth? It should be very common at levels 20-40.
But yes, with a ReVi lab total of 24, it will take 5 seasons to invent Aegis of the Hearth. It would be faster (and arguably cheaper) to go out and buy a lab text for a pawn or two of vis.
Of course, experimentation and/or help in the lab could improve the lab total.
Also, an alternative to a lab text that could give you access to an Aegis is a casting tablet.
It depends on the saga, but for a variety of reasons the level 20 Aegis is probably so common a spell that gaining access to a lab text and/or a casting tablet through the Redcap network should be extremely easy and cost a pawn of vis or two at most.
It could even be said that without such a labtext (if the magi haven't already the spell !), there would not have been a covenant between magi.
They all come from somewhere, and their parens/amici would likely say to them (if they were known to be the distracted kind of magi) "take this aegis labtext, I'm sure it will be useful."
After all, giving gifts to new covenant is a pretty common practice.
I would say that this labtext (20) is the most common spell in the order when it comes to number of copies available in libraries.
Yes there is: Penetration!
I know this may spark a heated debate as to whether Aegis needs to Penetrate. But IMHO as there are no ruled precluding it from the normal rules, it does. Same as Wards, which have been clarified to need Penetration.
Which is why we cast Aegis of the Hearth using Wizard's Communion
And I agree, having the aegis need penetration is THE reason to have all the magi collabote through WC to cast it, which, IMO, is more mythic. Otherwise, you just handle it to your ReVi specialist while his covenant mates sit on their collectives asses.
That's over-interpreting this line in an adventure: "If the Aegis is of sufficient Level and Penetration, the covenant may end up fighting the Waimie's offspring outside the covenant."
It shows an author aware of writing an adventure for a mature rules system with different entrenched variants: so he settles for "sufficient Level and Penetration" and lets the SG decide what "sufficient" means for her troupe.
Something about the Aegis Christian was proposing was bugging me, and I couldn't put my finger on it. Technically, penetration is described as Casting Total - Spell Level. I've never seen any spell or effect that includes penetration in the casting total itself. I would think it would have to be a House Rule to do this, as I don't see any room within RAW to make it work. As a house rule, it's fairly reasonable, though, because something similar is done for devices.
Right, which is why I said it's a house rule, and it is clearly a bit of an end run around penetration rules, generally. Maybe it is possible for wards and the Aegis, but not for other spells, because Wards and the Aegis are stationary, or fixed. High level wards and the Aegis are next to impossible to cast (even by specialists) without cooperation of others. That can be both good and bad.
Aegis and RAW is a good example, how a rules system made by intelligent people can still fall prey to its own complexity.
That ArM5 wards should penetrate, was found by the line editor late 2005 or early 2006: about two years after ArM5 was published. During all the calibration and playtesting wards had been seen as not needing to penetrate - and both the Berklist and this forum resounded with some explosions when that changed.
Only 2007, in HoH:S p.113 left box, the need for wards to penetrate was written up explicitly - thereby also creating an Ex Misc tradition doing wards better, and directing normal Hermetic magi to other kinds of protective spells. Since the 2004 rules calibration for normal ArM5 Hermetic wards did not change, these quietly disappeared from game use.
Just that Notatus' Aegis was too important to be handed over to some Ex Misc specialists. No clarification about it was ever published. Errata to recalibrate it have never appeared. So every troupe fends for themselves here, and needs to find their own equilibrium between campaign paranoia, real threats to the covenant, dedicated studies of covenant members and available vis. And once - typically early in a campaign - that equilibrium is found by a troupe, they stick to it.
Whenever Matt Ryan and Timothy Ferguson, arguing that canon or 'RAW' are for authors only, need an example from ArM5 (and not only Apprentices ), the Aegis is an excellent one.
One Shot, can we keep this on topic without dredging up the penetration debate here? You have your view, you think you're right, and you think that anyone else who thinks differently is wrong.
In this instance, if an Aegis does not need to penetrate, then building penetration into the spell is useless, the level will still be 20 and no added benefit is gained. If the Aegis does need to penetrate, then building penetration into the spell is a HR, and it might have unintended side effects, if it can be done for other spells.
Whoa, jump back!
Penetration built into spells - where did that come from? Not from me, that's for sure. I re-read my posting and could not find anything suggesting this.
Although I do find my posting lacking any reason at all for why an Aegis could benefit from a lower base, even when is must count as lvl 20 at the very least. Sorry, I'm just off my trolley, I got it bass-ackwards. The lower base than 20 merely makes the spell less effective, providing a lower penalty for foreign casters and keeping out lower Might creatures. But it still costs the same amount of vis, and Penetration is still calculated from lvl 20. What the deuce was I thinking?
My bad. But please just tell me I'm bonkers - I get confused when I'm suddenly credited for claiming something I can't recognize :S
Well, it was implicit in a discussion regarding designing a less effective Aegis of 10th level, and then filling it with other "stuff" to get it to 20th level, the minimum level of an Aegis. You didn't state it directly, but I didn't see any other way to read it.
A ward is cast on what it is protecting, not what it is keeping out, so how does penetration make sense? Sounds to me like a single author botching their rules roll and Atlas trying to cover the lack of editorial oversight.