Our group just got our hands on Hermetic Projects. Pages 94 and 95 discuss Aegis of the Hearth.
As far as we understand it, to temporarily (diam) suppress a level 35 AotH with Guttering of the Home-Fires you need a level 40 version of the spell (AotH < GotHF/2 + 15). But dispelling the same AotH requires a level 20 Removing the Hearth's Keystone - or less (AotH < RtHK + 15 + stress die).
Thus dispelling a level 35 AotH requires a simple spell and a PeVi casting total + penetration bonus of just 55. Attainable for a specialist with a little vis.
A level 20 AotH is dispelled with a casting total + penetration bonus of 25 and is thus useless against magi (except unprepared apprentices - maybe.)
The +3 Magnitudes is added before dividing by 2. So to suppress a Level 35 AotH you need a GotHF of level 55 : (55 + 15) / 2 = 35.
Yes, it is easier to dispell than suppress. This is a consequence of the PeVi and ReVi guidelines in the core ArM5 rulebook.
Sure. This is assuming that you have invented the formulaic spell.
There is likely strong social pressure to not make it well known that you can do this. So, even if you can do this, you wouldn't want to do it often. As, stabilising forces within the Order will think you are a risk to the stability of the Order and declare Wizard War on you.
Also, if you dispell an Aegis during Wizard War, then you likely need to be fighting Wizard War simultaneously against all the (magi) residents of the covenant. Otherwise the non-involved magi may claim that you are depriving them of "magical power". And if you are making a nuisance of yourself or appear to be too dangerous, the Tribunal will have strong incentive to find against you. Depending, of course, on the context of the Wizard War.
Yes, but a level 20 AotH is largely useless for magi more than a few years post gauntlet anyway. An Aegis doesn't stack with a magi's own Magic Resistance, and most magi more than a few years post gauntlet will have a personal Magic Resistance greater than 20 anyway. A level 20 AotH usefully shields grogs and keeps out minor critters, but its faux Magic Resistance against incoming attacks isn't of big benefit for post-gauntlet magi.
Thank you very much for your clarification, Richard!
I understand that there should be strong social and political deterrents against abusing RtHK.
We enforce that AotH must penetrate Might to be effective as a Ward in our saga, so we need to take these new spells into account when deciding what level the AotH should be for our Covenant. A higher level AotH will thus be more effective against magi, a moderate or lower will be a more effective Ward.
Unless I am mistaken, the above comment is wrong - or misleading at best.
An Aegies doesn't excactly stack with a magi's Magic Resistance (nor Parma Magica btw), since it works in different ways; it does not grant Magic Resistance. On the other hand, this means that being protected by an AotH would always be beneficial to a magus, no matter how high his Form Resistances or how impressive his Parma. Thus, claiming that it isn't of benefit for post-gauntleted magi is not true IMO.
The AotH reduces the casting total of your foes, which is always a boon. Even a low-level AotH, such as the level 20 discussed in the above (which is by far the lowest I've ever seen), would reduce an outsider's casting total by 10. Which is similar in magnitude to; defenders appropriate form score at +10, defenders Parma Magica ability at +2, attackers appropriate form score at -10, attacker burns +5 pawns for penetration for naught.
Thing is, AotH does several things. When spells are cast from outside the area of the Aegis, they are indeed resisted, while if the outsider has entered the area of the Aegis it does indeed lower the casting total. To ignore either is a mistake.
However, if a magus outside your Aegis casts spells against you while you are inside your Aegis are indeed resisted - this is the situation considered by mr Love.
You are considering specifically the situation were the aggressor is inside you (friendly) AotH - these are not the same situation.
As a note aside, AotH is a ritual, so the above level of 20 is presumably chosen because it is the weakest possible AotH spell.
Any level of AotH is useful, from 20 up. For protecting a magus' person, any magus who is serious about their self-protection can muster magic resistance higher than 20 with relative ease.
All Parma and/or form resistances do is protect yourself. It doesn't protect your lab, your grogs, your books, all those numerous arcane connections that you leave lying around your own bedchamber, etc. Aegis covers all of these. A level 20 aegis requires a hostile external caster to overcome an additional 20 penetration - something that they'll probably laugh at for their combat spells, but something that may well matter when it comes to scrying or stealing things via magic.
This is one of the things that irks me the most in the Ars system. And I have no idea why it is there. A "ward because the creature is too powerful to destroy so I trick him into a trap" has been a staple of fantasy literature and legends for ages (trap, not destroy). Instead in Ars we just go around and smack the supernatural being in the forehead.
Yup. But the problem, IMO, lies in that might strippers are very powerful, especially with multicast
Which is why I love giving critters a "Might soak" based on their Might score. Like twice (Might/5), or more.
Makes these multicasts lvl 05 DEO kinda useless against anything with might higher than 10.
This might be combined with an idea I had once, which was that multicast spells cast at a single target only worked "as if" the base level was increased by 5, just like a spell's description might speak of a miriad stone shards doing +10 damage, not 1000 times + 0 damage.
=> 4 multicasts lvl 10 DEO would instead work as a lvl 10 + (5/copy) = 25 DEO.
Nice idea there. The 1 target, 1 effect per round is cool thinking.
We just multiplied everybody's Might by 4 when dealing with hermetics. (it is kept at normal levels for non hermetic magic since we have not found them to be so terribly out of sync so far). So your average nymph has might 60 now, not 15. Archangel Michael would have might 240-260 (cant recall his exact might now) and the demon in the rulebook 200. Much more difficult to beat them now by brute force. The whole might system is somewhat out of sync with hermetic magic, this is why we need to introduce house rules. All the troupes have something of the kind to reduce the might of hermetics or increase the might of supernatural creatures.
I think you just fixed multicasting, The Fixer. That's a very interesting house rule.
That is a lot. I generally think Might x 2 is enough. Might x 4 means that even a lowly Might 5 faerie [say] is almost untouchable at gauntlet, walking around with Might 20 in a foreign aura; this seems rather excessive to me. And at the other scale, giving Michael Might 200 seems to work fine as long as Wizard's Communion doesn't apply [that's what broken].
Obviously your players do not have casting totals of 40-50 at gauntlet
Penetration multipliers are so common that multiplying Might by 4 has not stopped our characters from organizing a dragon hunt per decade across Europe. It is quite an event, with magi from around Europe attending the organized party. Wizard's communion is just ONE of the many multipliers. Others include magic items (even with the +1 penetration per point) and arcane and sympathetic connections. In the end it means that the Might score of a creature is quite irrelevant if you have some time to prepare to face it.
But yes, 40-50 was definitely at the higher-end, and those players typically had very little Penetration as they used high-level spells. Still, I can see how Might 20/Mightx4 would work with such power-levels
Not mine. Casting total of 40 is designed towards penetration. The spell might be as lowly as crystal dart (version XL for added damage) or a POF. They work under the premise that with 30 spell levels and a shield grog they are more or less immune to mundane attack 8except against hordes of enemies) so they have to concentrate on one or 2 spells to deal damage to the supernatural creatures with a medium range spell (level 15-30) designed to strike true (penetration or high aiming). Rest of spells in utility stuff.
The Might x4 was introduced on player demand, since they found it boring that they could destroy HELL (boundary x10) with a concentrated DEO cast via wizard's communion and using captured demons as sympathetic connections. Or some other kind of pub crazy talk we had some years ago. A player actually ran the numbers and amazingly it COULD be done. God allowing it et al, of course. Minor details As you can see dragons were minor nuisances considered fair game for a "day out practicing falconry" (or some other crazy talk like that) when you consider that level of crazy projects and pushing the envelope. they rarely do what they say they COULD DO, but that does not mean they do not THINK about doing it
OTOH if wards don't need to penetrate then the minimum effective ward requires a casting total of might - 9 but the minimum effective might stripper requires might + 1 so containment is two magnitudes easier to cast.
That doesn't help with suppression vs dispelling but you might explain that by saying most spells are not designed with a standby switch so suppressing them without breaking them is more complex and difficult than just hitting them with a PeVi hammer until they are thoroughly gone. The advantage of suppression is not ease but the fact that when you are done there is no evidence that you interfered with the spell.
I like this.
In My Saga I limit the non-penetrating wards to stationary, Ring, Circle, though. It fits well with my feeling of the stories and myth that a protective (or binding, depending on which side of the ward the baddie is...) circle is much more powerful than any generic protection.
And as you say it makes catching or protecting against things easier than flat out destroying them
It makes a bit more sense now, although I'm still not following the:
This is one of the things that irks me the most in the Ars system. And I have no idea why it is there. A "ward because the creature is too powerful to destroy so I trick him into a trap" has been a staple of fantasy literature and legends for ages (trap, not destroy). Instead in Ars we just go around and smack the supernatural being in the forehead. 
The 1 target, 1 effect per round is cool thinking.
Thanks a lot.