I had the idea for a saga where there was a consistent unstoppable threat that was always at the covenant. Maybe a regio with a Might 100 dragon or something. The covenant would want to be there for the High aura and for Vis sources.
What I can't think of a reasonable explanation for is why they wouldn't just have a large portion of the covenant outside of the regio.
I feel like the tension would fall off very quickly if they could just be in their pleasant country side castle and only really needed to worry while they were in the lab or when they were collecting Vis.
I was thinking that maybe the regio entrance was inside a church or something, St.George having locked away the dragon, sanctifying the site and thus shunting the Magic Aura off into a Regio. Actually that is pretty good...
Either way I would probably want a few levels so maybe the next level down was the home of hostile spawn of the dragon and the various virgins he kidnapped through the years, ensuring a constant, powerful, magic resistant enemy.
Obviously such a saga would be at the far end of the High/Low Fantasy Scale.
I suppose the remaining issue is why would they live there rather than simply going in to plunder the vis while living in an inferior covenant? Have it is one of the dense tribunals where claiming two auras would be difficult? Make it valuable enough that you would be fighting every time you went? Have the lower level denizens beat you to the punch and gain power?
Does any of this make sense or am I missing a giant hole?
Unnatural Law: This site is the home of something special. If you harm that home in any way, your own home will be threatened, no matter where it is.
So you might as well live with the monsters.
In fact, you're doing a favor for the Order. Your covenant prevents anyone else from pillaging the site, thereby bringing ruin to their towns or covenants, and by harvesting resources from the site and selling them, these resources become safe and available to anyone else. Laundered, if you will.
Alternatively or additionally, the site might provide extraordinary benefits above and beyond a high Aura. Perhaps if you stay there for 3 seasons or more in a year, the first Warping Point that you would gain next year is not gained. Or for every season you have the guts to stay there, you get once 1 Confidence Point (temporary) and one 'xp' that can increase your Confidence as though it were an Ability. (Stay there for 10 seasons, and Conf 1 becomes Conf 2. Stay there for 100 and you now have Confidence 6.)
Or perhaps once you plunder the site you are cursed to suffer Deprivation if you don't live there for at least 2 seasons per year.
Or perhaps the site was once sealed, but the covenant founders broached the seal, and now the monsters or threat will escape to the normal world and wreak havoc unless there are at least 3 magi within the regio at all times. The founders escaped conviction of violating the Code by pointing out that they have not yet brought any ruin upon anyone. The Tribunal agreed but obligated them to guard the site or face conviction, and that obligation has been passed down.
Normandy - a covenant has rights to resources within half a day's travel, everything else is held in common for the Tribunal and is distributed following the Tribunal games. Therefore, you want your covenant within a short distance of the best vis sources. If within half a day of the regio of doom is almost as dangerous as being in the regio, you way as well live in the regio and get the defensive advantages.
Thebes - as every covenant needs a supernatural patron, it may be worth settling such a dangerous site in order to try and study this creature and work on persuading it to be your patron.
Rhine: The "Guardians of the Forests" clause in the peripheral code gives a vague obligation to protect magical sites and slow mundane intrusion. Maybe a Tribunal ruling said you could settle this area - as long as you protect this site from mundane intrusion and try and distract the monster from killing mundanes too freely?
Regarding the original post, I had a similar idea which went into an issue of Sub Rosa - the Covenant of The Green Knight. Like in the story of Gawain and The Green Knight, when on the Knight's lands you must share a portion of what you find with the knight. (In one version of the story, the Knight shares a portion of his hunt and Gawain shares a warm embrace or a kiss or whatever he gained from spending the day flirting with the Knight's wife). In the Hermetic version, the Knight is a faerie landlord who controls an area rich in vis, but you must share a portion - so some of the vis is left behind, unless you want punishing. The covenant claims they are searching for knowledge, and so they get round the restriction by leaving frequent gifts of written up knowledge for the Knight. Visitors are encouraged to write of what they have found. This has built into a large library of vain tractatus, accessible at the price of having to leave some writing of your own behind.
There are also a lot of tribunals where staking claims has no real enforcement, so you need to either keep it a secret, move in, or have a contested vis source. In fact I believe that applies to most of them.
Have you considered the covenant's placement to be bound by some sort of curse/geas?
With Unnatural Law or Warps to a Pattern, the covenant ground itself could resist attempts to locate the majority of the work elsewhere, either directly or by affect on covenfolk without parma.
Or the whole covenant could actually be "owned" by a faerie court and have to live under its rules lest it bring down the wrath of powerful fae (and possibly violate the Code). Or the deal could be with the dragon.
If you want something Divine, the covenant could be through a papal grant to a Jerbiton mage on behalf of his sainted relative -- literally. The magi actually derive authority and income from maintaining a holy site, AND the saint shows up to bother them.