A note on Aegis of the Hearth from Project Redcap - Varies spell as written in 4th Edition.
Aegis of the Hearth
As written, the Aegis of the Hearth simply is not worth the cost in raw vis it takes to cast. Not only is the range unable to cover any but the smallest covenants, but the effect of the ritual is also quite weak. Any creature powerful enough to be anything other than a nuisance to a covenant can waltz across an Aegis with no penalty. Even the spells the Aegis was designed to protect against (like those that teleport a magus inside), are higher level than all but the most powerful versions of the spell.
I can't imagine that most covenants would spend the Rego or Vim vis necessary for a spell that has been aptly described as nothing more than a mosquito net. Yet the idea of the Aegis as a priority for a covenant is well established in the game. To reconcile this, I have introduced a more powerful version of the spell in the Friend of Mine Enemy saga. The protection it provides is enough to be valuable to covenants, without providing an inpenetrable shield for magi to hide behind. In addition, I've added something that allows covenants to personalize their magical protection somewhat.
Aegis of the Hearth: Gen R: Spec., D: Year, Ritual
A covenant can be a hazardous place to live; magi, being extraordinary folk, tend to make extraordinary enemies. Magi protect themselves with the Parma Magica, and they use a similar kind of magic to protect their covenants.
The Aegis of the Hearth protects a covenant from spells and intrusion by supernatural creatures. Any spell affecting an area covered by the Aegis (originating from inside or outside its boundaries) by any magus not involved in the Aegis Ritual is hampered by the Aegis. Furthermore, spells that scry on anyone inside the Aegis, or attempt to send an object there (like teleportation spells), are also resisted unless the caster was involved in the ritual. If the "foreign" spell cannot overcome the Level of the Aegis + 5 + a quality die, it fizzles out, though vis and fatigue are still spent, and any botches are still rolled.
Any creature whose nature is tied to one of the four supernatural Realms cannot enter an Aegis unless their Mystical Might + a stress die is higher than the Level of the spell. A creature who fails to enter the Aegis cannot try again for a duration of Sun.
A creature who is able to enter the Aegis usually has the Level of the spell subtracted from their Mystical Might score (though it cannot drop below zero), so even if they penetrate the border of the Aegis, they may be too weak to harm the magi within. To avoid this penalty, the creature's roll to enter the Aegis must double the Level of the spell.
Note that Man, through Free Will, can choose to align himself with a Supernatural Realm, but his nature will always retain some independence from it (else Redemption would not be possible). Exotic magi or other characters with Mystical Might scores are therefore not affected by the Aegis (though their spells are).
The Aegis is normally cast upon the walls of the covenant, though every extra pawn of raw vis can extend this range by 10 paces. Anyone inside its boundaries at the time the ritual is performed is considered included in the spell, unless the casters make a conscious exception.
Despite the protection given by the Aegis, some covenants prefer to add more spells to their defenses. The special way in which the Aegis Ritual is performed makes it possible to weave other defensive spells into the fabric of the Aegis, with effects similar to The Waiting Spell. One extra pawn of vis must be spent for each additional formulaic or spontaneous spell added to the Ritual (adding Ritual spells is not permitted). Only spells of Levels equal to or lower than the Aegis may be added, and the total number of spells added cannot exceed the Magnitude of the Aegis, nor the number of magi involved in the Ritual. It is often customary for each magus involved in the Ritual to add his or her chosen spell effect in turn.
Unlike The Waiting Spell, the spells woven into the Aegis are discharged whenever a foreign magus casts a spell from within it, or a supernatural creature succeeds in crossing its boundaries (the Aegis can never affect anything outside its border). The magi cannot specify different conditions nor use Intellego spells to affect only certain targets. The spells discharge simultaneously, though if two spells of the same type are cast, only one is used up; the second remains in waiting. Common additions to the Aegis include warning spells and spells that launch an attack upon whomever disturbs the Aegis; the Storyguide should use common sense in determining which spells are appropriate.
Anyone directly invovled in the casting of the Aegis can invite another within its boundaries through the Law of Invitation. This requires nothing more than a conscious effort on the part of the magus, combined with a formal invitation. Once invited inside in this way, a person (or creature) is considered part of the ritual until the spell is recast.