If you have a 3 tier magic regio, say level 3 aura on top, a level 2, then a level 1 in the mundane world. Can you build a covenant on level 3 and put farms/servant quarters on level 2?
Does the agies only cover one level, or all 3? How does the boundary qualify? I am of the opinion that an agies would cover all levels but it hasn't really been discuses as far as I know.
How big is an average regio without taking vast regio? Vast regio says 5 miles across, but there is no lower limit.
Yes, you can. Generally there is some kind of shadow of the iupper levels in the lower levels, so if you have a tower in the level 3, you might have a heap of stones in level 2 and a large boulder in level 1. Or something like that. Not necessary, but has been the case in a lot of regios in the official setting
Only covers 1 level.
This varies a lot by saga and specific regio. I have no answer right here. Would need to check, but maybe in the core book you can find an answer, where it describes regios? I would have put an answer to that there if anywhere.
As to the shadow effect, as you mentioned, a tower might be a ruin or a pile of stone on the lower levels, what happens to the upper level if you clear that stone? In other words, is the revers true that effecting the lower levels will effect the upper ones? I think there are examples where this sort of happens, regios in cities where buildings are mirrored in the regio. (Sorry I don't have my books with me)
I know I am going a little off the beaten path. But I smell some fun possible story hooks. If you clear the stone you might damage the upper structures. Does it just slowly reform over time making farming a more difficult prospect? I'm guessing this is more of a case by case thing, but linking regio levels might be a fun minor/major hook (depending on severity) either to add or just to make an occasional nuisance for background story. Or is that sort of thing to weak for a covenant hook?
Yes, each is their own "pocket reality". They are interrelated but most actions in one do not factor into the others. I like to think that they started as the same when the regio fractured into separate levels, but then actions and time on each leads to the content being different. Actions that harm the regio itself should factor across them (was it RoP:M which had the rules for increasing and decreasing regio?).
In the "normal" realm the aegis protects within it's boundary, and if the regio covers the same relative space then it would be protected from effects seeking to penetrate into it from outside the Aegis in the normal realm (which is normal use of the ritual). So yes it partially protects from "outside". However if the effect originates from within the Aegis, or between layers then no - as only the layer which has the Aegis cast actually gets the protection. That does not stop other regios from having additional Aegis cast for other reasons.
I don't think the aura has to reflect the size. Nice if is does, but also more than happy if it varies.
It's not covered by any explicit rule, I generally think that you can't put a single Aegis around something if you end up having to cross over your path when tracing the boundary, so if your regio has multiple exits, it might be possible to do this. But that's a YSMV thing.
Regio are generally considered to get smaller as one goes up in power. I think I remember reading that somewhere. The Boon is Vast Aura, not Vast Regio. But there's nothing to say that the top layer of the regio is bigger than the lower levels of the regio and/or the mundane level.
Thanks, ArM 5th says it is big enough to house the magi and coven folk, which amounts to 2 servants, 1 warrior and 1 craftsman per wizard. So that's pretty small. Maybe the maximum of a quarter mile across at most without the vast aura boon.
Absolutely. Assuming they are big enough, of course.
Up to the story guide. Maybe nothing, maybe renders the upper level inaccessible, maybe destroys the upper level. Could be different for different regios. If you want the PCs to figure out which applies to a particular regio, without doing the obvious experiment, then I suggest making rolls against INT + Magic Theory against some suitable Ease Factor (maybe modified by the extent/capability that the PCs have to observe the regio).
Depends. If level 2 is "inside" level 1, then an Aegis that covers level 1 should protect level 2. If level 2 is "not inside" level 1 then it won't. Up to you to decide which is which for a particular regio. Generally, I think it is assumed that small regios within a covenant are inside the aegis (and therefore covered). Otherwise having a regio in your covenant would be a huge vulnerablity (enemies could Leap of Homecoming into your regio without penalty).
Up to you. Somewhere between a room and few miles across, I think. Typically, they seem to be things like "forest clearings" (which can obviously be quite different in size).