Preternatural Tethers and AotH, along with other interesting details

Games Discussion Ars Magica
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The Saga I have been playing in has used the "Magic Auras" rules in Realms of Power: Magic since one of the founding focus of our saga was 'manipulating a Regio'. A few interesting observations have come throughout our playtime.

Growth of Preternatural Tethers

Firstly nearly any Covenant which has a stable location can easily reach a Preternatural Tethers total of 5 within the first century of its existence unless the SG leans very heavily on the No side of 'Can/Suggested/Might'. Many Covenants are built on powerful sources of Vis (some Tribunal almost require it) and/or ancient ruins which saw great magic which would have some degree already. While not universal, not many Covenants never cast at least a few rituals in the 50+ range. A common trope of having things like a flock of birds of virtue within a Covenant has been in official releases since at least 3rd edition. While the SG should say no to some things, why are you using the rules in RoP:M if they say no to nearly everything.

Any Covenant which uses a powerful Aegis (meaning level 50+) might be generating a 'Magical Residues' tether of 1+ every year. These Aegis are powerful rituals and should have a residue, but should it make all other Preternatural Tethers pointless in five years or less?

My group settled on a method to handle powerful annually repeated rituals by combining 'Magical Residues' with 'Magic Monuments'. Rather than generating a new tether every year we set the base score to the highest using the calculations in 'Magical Residues' and then add a bonus for long repetition equal to +1 for every century. We based this on Durenmar in which their standing stone is part of their yearly Aegis and is a Preternatural Tether 4. Weaker than level 50 annual rituals would eventually generate a 'Magic Monument' tether like this if Durenmar is an example to go by and tying the 'Magical Residues' for more powerful rituals to it seemed appropriate.

The Importance of Natural Tethers

Since the Preternatural Tethers of any Covenant will eventually drift up to 5, this making selecting a site with Natural Tethers important. The Natural Tethers are the biggest restriction on how powerful an Aura can eventually become since it is almost impossible to generate one. They are also limited to a maximum of level 2 each so it would require a site with at least three of them to hit the limit of 5. Even worse is that most of them will be only level 1, since all of the examples of level 2 are rather extreme and a Covenant might be situated on a site with one at that level. I would argue that Durenmar has only a single Natural Tether 1 (the beautiful valley).

If you total up the Natural Tethers, you can calculate the maximum Aura the site will eventually (likely centuries later) reach at that level +6. This is possible because a Covenant with Autumn or Winter Magical activity and casting any Aegis annually (since it requires more than the 3 pawns of Vis for a +1) will normally generate a 'Yearly Aura Modifier' of +4 barring a stronger Divine/Infernal Aura, Detrimental magical botch, or Vis Extraction. It has a slightly greater than 5% chance in those years of getting "Current Aura +1" when its Current Aura is equal to its Base Aura. Years where the Base Aura is higher than the Current Aura see this jump significantly (36%+ with 1 point difference, 67%+ with 2 point difference, etc) while years where the Current Aura is higher would require something exceptional to make an improvement or decline roll. I would argue that Durenmar is at this point, with a Current Aura of 7 and Base Aura of 6 from Natural Tethers 1 plus Preternatural Tethers 5.

This all really only matters for long running Sagas or when simulating long times (such as designing an old Covenant). It does tell us that most older Covenants will max out at an Aura of 7 while active and might eventually decline to an Aura of 6 after they are abandoned if on average the Order builds their Covenants on sites with a single Natural Tether 1 away from strong Divine/Infernal Auras.

The Dangers of High Aura Instability

What I am referring to as an Unstable Aura is one that has to roll on the "Aura Strengthening Table" or "Aura Weakening Table" every year.

Any Aura with a Base Aura different than the Current Aura is often unstable. It needs a 'Yearly Aura Modifier' outside the range of -3 to +3. With any magical activity this is mostly the case with a one point difference (and with lots of magical activity such as older Covenants with a 0 point difference) while without magical activity it must normally have a two point difference. A weakening Aura is not dangerous unless it is a Regio and very unstable, but any strengthening Aura is going to cause about 0.1 points of Warping every year to some part of its inhabitants on average.

A little Warping is not that dangerous, but what we have been talking about are Aura that are only slightly unstable. The danger comes about when they are highly unstable because of things like the Base Aura growing far faster than the Current Aura. Anything that would keep the annual 'Aura Strengthening Modifier' in the +6 or higher range. This situation can easily result in the Aura banking a Botch Die nearly every year which is a growing danger of triggering the forming of a Regio which will inflict 3 Warping points on everyone within the Aura and risk sending all Magi into Twilight. Depending on how the Regio forms, this might also scatter shot the Covenant all over. Having your defenses in the Regio and the Magi's labs outside of it is a bad thing.

Even worse the chance of another Regio forming will only get worse each year until the Aura stabilizes for several years. Since the Magi will have most likely all moved into the Regio (higher Aura and more secure) they are in danger of getting hit with another burst of 3 Warping (yea Twilight risk) and once again being scatter shot all over.

An unstable strengthening Aura with Regio might be able to be safely inhabited as long as it is not on the highest tier of the Regio. This depends on how your group reads the warping inflicted by a new Regio tier forming. If it affects everyone on every tier (including possibly the mundane tier) then no such luck. If it only affects people within the aura of the highest tier then lower tiers are safe. The second is how my group plays it since we wanted a long saga and knew our Regio would be unstable for most likely the whole play time. When your Saga is planned to span centuries having a steadily growing chance (start at 1% and increase nearly yearly) every year of a burst that can send all the Magi into Twilight seemed very bad.

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The maximum aura from preternatural tethers is +5, so how do you arrive at a natural aura+6? Unless the natural aura will improve it should max out at natural aura+5.
Though antiquity is mentioned as a natural tether, so it would seem possible that time can in fact raise the natural aura score, though if this raises the natural tether by 1/century it would seem that natural tethers higher than 2 should be fairly common, since there are certainly sites older than 200 years...

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You seem to have a slight misunderstanding and I will try to help explain. Please do not take this as me being donkey.

There is no Natural Auras or Preternatural Auras. What there are is Natural Tethers and Preternatural Tethers. You add the Natural Tethers Score to the Preternatural Tethers Score to get the Base Aura Score (last part in the middle column RoP:M, p 8).

The Base Aura Score and the Current Aura Score are two different things. The Base Aura Score is only used in one place, the 'Yearly Aura Modifier table' on RoP:M, p 10. Outside of this it does nothing and has zero affect on anything. It would have been less confusing if Atlas did not have "Aura Score" as part of its name, such as calling it something like Total Tether Score.

The Current Aura Score is what every book is referring to when it list things like "Magic Aura 6" or the effects of an Aura on some activity. Tethers have no direct interaction with it. They do have an indirect interaction by raising the Base Aura Score which would generate a higher modifier on the 'Yearly Aura Modifier table' and make it increasing more likely.

It is possible to have a location with a Current Aura Score of 0 and a Base Aura Score of 5 if you rapidly generated a bunch of Preternatural tethers. Of course as soon as a year passed the difference in the two would give a +15 to the "Yearly Aura Modifier" which would have an overwhelmingly high chance of increasing the Current Aura Score to 1.

Natural Tethers have what is effectively a maximum Score of 2. The first line in the third paragraph of 'Natural Tethers' (RoP:M, p 8) reads "The examples below describe only places with an aura up to a maximum score of 2, because individual perfect natural features have never been known to demonstrate a stronger aura." The SG might decide to create one, but would be beyond an 'individual perfect natural feature'.

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To be fair the book is sufficiently confusing that I often wonder if that author had a clear idea of what they were trying to say. Since the Base aura score is equal to the sum of the natural tethers score and the preternatural tethers score I tend to think of those as the natural aura and pretrnatural aura- a change in terminology, not understanding, which arises in part from the way the preternatural aura score is calculated which is massively non-linear.
Personally I have to wonder what would have happened if the rules had allowed for a base aura over 10 but not an actual aura over 10, where forces would be trying to increase the aura until it created a "regio" boundry into the magic realm...

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You are not the only one who wonders about what the author originally planned. The crunch is scattered about seemingly at random, much of it is inconsistent (maybe, might, possible), and it generates multiple terms only used within the chapter including one which changes a term used throughout the entire rest of the line (including the book it is in) into something else.

To answer the question in your first post now that I understand what you were asking, the Natural Tethers would not increase or change. The Current Aura can actually be higher than the Base Aura. The reason you add +6 to it when finding what an Order Covenant's aura will eventually reach is that it will form Preternatural Tethers 5 eventually (or quickly depending on the Magi) and with the activities of the Magi the Current Aura will eventually settle at 1 point above the Base Aura. So Natural Tethers # + 5 for the Base Aura and Natural Tethers # + 6 for the Current.

I believe you can actually do something like this using the rules as they are, though of course it would require the SG to say it worked. The Current Aura can exceed the Base Aura, so any increase which would push the aura of the top Regio tier to above 10 can be treated as that level actually becoming a boundry into the Magic Realm. Or just ignored, if the SG does not want to deal with the Magic Realm.

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One thing I forgot to include within the OP is that any area which is unstable will grow in size and a useful way to determine how may the "Several Yards" is for the 14 result on the Strengthening and Weakening tables. Since you already have a modifier calculated by all the influences on the Aura, using that modifier as the number that the "Several Yards" equals to means that the Aura will grow or contract based on those influences. This will give a result of 4 to 9 Paces (yards to paces should be errata) added to the diameter.

This also provides an additional effect for when an SG is designing old Covenants and other locations in which the Aura was unstable for a long time. Since the Aura Growth result will come up about ~10% of the time, use 0.4 to 0.9 paces per year of growth when working on a long period of time without having to roll yearly. The lower end of the range should be used for places which experienced safer growth.

Once again we look at Durenmar as an example. We know that their Aura has grown in strength and in size since its founding. We also know that this growth has been fairly safe since it has been around for over 400 years and not formed a Regio. Using the bottom end of the scale for size growth estimates, we have 40 paces per century. We do not know when their Aura became stable at its Current Rating of 7, but most likely that event occurred a century or two ago. So the total size their Aura has grown is most likely 80 to 120 paces from its original size since its founding.

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keep in mind that just because an aura has become stable does not mean it will remain stable, since changes in magical activity can destabilize it. You could have an aura with "growth rings" of stable periods that can be tracked (at higher levels) based on how much things in the area have warped.

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Very true, which is why I recommended using the low range of possible growth when calculating it over a long period of time. 0.4 or 0.5 "Paces per Year" average would most likely be made up of many periods where more rapid growth occurred and even more where no growth happened at all.

The "Growth Rings", which can be judged by Warping, is a very interesting idea. It is a small detail that PCs investigating a site might discover when trying to determine when some calamity occurred.

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