Seasonal analysis should certainly work, though it's a bit impractical for an enemy covenant's Aegis. I was wondering if there was something easier: it feels as if there should be, as an Until condition has to be woven through the spell. (Of course, an Aegis would resist the spell, making it harder.)
I like Lee's view that there should be a story to beat the Until condition. It feels to me that Until is inherently Faerie-related, and while it could be brought into core Hermetic effects, it would retain that feature. So any cheesy conditions such as "It lasts until someone trisects an angle with straight edge and compass" or "it lasts until ninety nine cheese makers with glass eyes sing for forty hours non-stop at its border" would just fail.
I tend to be very rules based and I wouldn't allow "until I wish it to end", it would need to be some kind of event or action that would trigger the end, and one that cannot be effectively made eternal through the simple expediency of killing the caster.
Wizards’ Boosts Duration Until (AoTE)
MuVi 25
R:Touch, D: Mom,T: Ind, Ritual
You cast this spell as another spell of a level less than this one is cast. The effect of the other spell increases 5 levels in power, but not past the level of the MuVi effect. The effects of the extra 5 levels of power changes the duration of the Aegis of the Earth ritual from Year to Until. There are many versions of this spell, one for each specific type of magic such as The Aegis of the Earth or a hermetic form . There are other versions of this spell, each of which affects one of range, duration, and target, for any hermetic Form but only works on effects integrated into the hermetic frame of magic. This does not allow spontaneous or formulaic spells to reach Year duration or Boundary Target, unless the Wizard’s Boost is a ritual. This ritual does not perfectly integrate into hermetic theory as it changes the parameters of the Aegis of the Earth which is not typically possible. It is the result of an imperfect laboratory experiment and side effects have been documented such as making creatures invited into the Aegis feel uncomfortable or even sickened. It has also attracted the attention of undesirable creatures. As a result, the ritual is not widely known in the order and is only known to be found in the great library of Durenmar in the restricted section to be consulted by academics doing research on the Aegis itself.
(Base Gen +1: +1 Touch)
Hammer of Dispelling of AotE
PeVi 50 (85)
R:Touch, D: Mom,T: Ind, Major Item
This effect dispels an AotE of up to the level 70. Note that this spell uses the Perdo Vim guideline, which dispels magic effects of a specific type (ArM5, page 160). AotE is an example of a magical effect of a specific type, which all Hermetic magi are familiar with. This is why Wind of Mundane Silence (ArM5, page 161), which dispels all magical effects, is effective against AotE. This spell does not dispel Magic Resistance generated via other sources, nor is this spell effective against any other sorts of magic. A few of these hammers were used during the Schism war. Original labtext was created by Antonius of Tytalus just prior to his house’s purge as a means of warning to Alliances that were getting a bit too testing for his liking. Following his fall, house Guernicus kept the labtext well tucked away until it was needed again. 3 hammers were created. One for house Flambeau, one for house Tremere and one for house Guenicus. Each was created with an effect expiry of 1 year allowing a lab total of 94 to create the effect in two seasons. One to open the item & another to invest the effect.
(Base 50: dispels magic effects of a specific type of the same level or less + 4 mags + stress die or +5 if object, +1 Touch, +35 Penetration)
I do think the usual practice is that each mage of the hostile covenant declares simultaneous Wizard's war on single magus on the target covenant with possibility of several wars on single magus. This is to avoid the accusation, and to imply the grudge is between covenants. The House Tremere uses House champions doing the same when they decide to get rid of some opponent through ToL: Houses of Hermes boons use.
Good way to get every one of the declaring Magi marched.
It does not matter if another Magi you are working with has declared Wizard's War against a different Magi if you have not. To attack a Covenant you must declare a Wizard's War against every member of that Covenant. To legally attack Covenant assets you must declare against every member of said Covenant. So in the scenario you described you have multiple Magi (illegally) attacking other Magi they have no valid Wizards War with and (illegally) attacking Covenant assets.
If A declares on Z, B declares on Y, and C declares on X. Any actions A takes that affects X or Y, any action B takes that affect X or Z, and an actions C takes that affect Y or Z are illegal. Since Covenant assets belong to X, Y, and Z, any action that affects those assets is affecting the power of all three and thus requires a declared war on all three.
If the attacking Magi declare on every member of the target but one, then if they damage any Covenant assets (including AotH) then they have committed a crime.
Any actions besides defense. Because if A declares on Z and draws Z into a trap on A's home covenant then other covenant members may help to defend their covenant from Z.