You suspect them of being an enemy, but aren't sure.
You suspect them of breaking the Code.
You suspect them of, intentionally or not, doing something that threatens your interests.
You want something they have, and aren't above doing whatever it takes to get it.
You want to gain leverage over them, for whatever reasons. (From future Certamen to Tribunal votes.)
You're a Tytalus, and just don't care.
Purely by accident, if they aren't clearly Hermetic.
You just don't like them, personally. 8)
This begs the question of who told the magus this? As opposed to the player knowing it...
It is, fittingly 
, a munchkin approach to gauge all your magi's efforts in the light of what will be used or not in terms of meta-story concerns.
My players can righttfully expect and demand from me that I present them with interesting stories with fairness toward their characters and their strenghts and weaknesses. But at the same time I expect from them that they make believable characters who spend their seasons with integrity and with an eye for what moves their character and not what will mini-max their stats/achievements.
I wouldnt mind players never letting their character spend one single moment, much less seasons, considering how to defend their sanctii, as long as this is due to reasons of the character and not against it. Would for example a deeply paranoid and seclusive character forego defenses simply because the player knows they might never come to bear against any foe?
It is a splendid idea - and I see from the thread that many have shared it. I had a Criamon NPC have one too. It was invested in the brass knob of his door - and it was made so that if you turned it the normal way the spell would trigger and if you turned it the opposite way it wouldnt. It fitted his askewed perceptions - and in time it made the grogs who served him most to warp faster than the rest...
In terms of defenses the same magus, being mostly a Rego and Terram specialist, had a huge brass band (no - not that kind of brass band ... though he probably would have felt at home in later days St. Louis) embedded in the wall of his round tower chamber. His finest defense was a pair of animated Circle/Ring ReTe bronze skeletons (each in ancient Hellenistic armour) still guarding the place many years after he disappeared..
I'm not sure a circular band around a lab is a good idea. Sure it allows you to anchor circle/ring duration spells but it also allows an intruder to cast ring duration spells on your sanctum. Unfortunately we don't currently have many good rules for sanctum defenses. I'd think though
- Circles/Rings that you can use and the other guy can't
- Wards against Mundanes and
- Anything that boosts your casting score and penalizes and intruders
would be popular. On the other hand inscribing the runes for CrVim on your sanctum door with the message in Latin "come inside uninvited and you will visit the twilight lands" might also work.
Actually simply allowing a magus to use his sanctum general quality and specialty bonus's for casting totals and penalizing intruders by the same amount would make for a very good defense, it could get a bit silly though when it comes to casting ritual spells.
Stephen
That is true. I guess it comes down to first of all the the character making a consideration of pros and cons of the defense in mind, but also to the fact that magi might not always be perfect...
However there are many advantages of a circular band (overcoming bothersome problems with durations being one thing). So many that I would even claim that most magi would benefit from at least one fixed circle in his lab for various purposes in his daily work or in extraordinary times.
And finally I do not think a circle is to more a detriment than an advantage to the resident magi - as the circle still has to be traced during casting of any spell about to benefit from it. The clever magi would ensure this couldnt be done from without, whereas the not so clever one might even be in trouble simply from inhabiting a round tower and having an ingenous enemy...
Until you get unlucky and run up against a magus with the right mystery virtue that all rings are linked. That said perhaps the covenants example of a ROUND tower needs a rethink.
Stephen
Actually this was another magus in a NPC covenant, but our own covenant actually also has some round towers in it. You cant guard against anything. Come to think of it, I might make a possible future story out of that.... 
Envoking Noble's Parma I'm wondering whether lving inside a circle's effect, even if it is not something affecting you, would add to warping....?
My house rule is that if you're using a ring as a cheap way of not investing a device, then you will gain warping. I tend to be generous to players who invest time or resources into doing something rather then take the cheap way out.
I've so far had no players do it - only a NPC and his later fate easily falls in line with having had plenty of warping...
But I'm certain that my players, should any of them opt for that posibility, wouldnt mind having some fun out of such warping. I'm not certain it is so much cheaper when it comes to time after all - the spells still needs to be invented.
Well circles and warping are a hard question. According to the Ars 5th rulebook Wards do cause warping. (Though it is unclear if this means circular wards or enchantments on a person). That said I'm pretty sure there is a rule somewhere that circular wards don't give warping, as the magic only effects the circle.
As for not having the invest devices there are examples in the RAW of various light and heat spells being cast upon very small circles (I believe the example was a circular ward against flame on a circle inscribed on a candle stand in a library.
Edit: and on that note Covenants page 104 says:
"The most popular type of sanctum defense is the ring and circle ward. Wards against mundane things, like people, pests and fire, are easty to create and cost no vis. Cirle wards at entrances, unlike spells cast on the Room Targets, do not warp the residents of the warded space"
Stephen
Cheers for the quote!
I think that the quote implies that if one puts a circle ward just around the door of a room then someone in the rest of the room wouldn't get warped. I don't think that it frees all circle spells from warping. (My apologies if I've missed the point of the discussion and we're all in complete agreement on this.)
Excessive ease of warping is one of the things I don't like about fifth edition. I wouldn't have a circle ward caue warping, or even a room ward for that matter. The magus is not being constantly affected. Let us assume that the ward covers their lab, sleeping chamber, and guardrobe are all under the same ward. There are still many things that can get a magus to leave for a few moments at a time. Getting food, borrowing ingredients, covenant meetings, and so forth.
For magi who use Enchanted Device wards, I would allow them a Characteristic bonus for Lab Magic Item, say +1 Safety for every full 20 levels of a specific ward.
According to the rules for warping on p.167 you need to be continuously under the influence of a mystical effect. I don't think that being inside an area warded against demons "influences" a non-demon. My interpretation of course but I'd ascribe the text Sdelear quotes as a misreading of the rules for warping that crept into a supplement.
I don't think that "excessive ease of warping" is an accurate criticism of the fifth edition warping rules. Naturally you might disagree, but I'd encourage you to give the rules another read and see if the problem isn't what you think it is.
I understood it the same way, Erik.
I also would not consider a ring effect to generate warping unless the magus was somehow included in the target/object of the spell. A ring ward vs. whatever, no. A ring that allows the caster to levitate up/down through the various levels of a large sanctum, yes.
Remember in 'Circular Ward vs. Demons', ArM5 pg 162 it says the following:
[quote="ArM5"]
Some mage cast this spell before going to sleep at night.[/quote[
I'd say that implies a common usage and lack of warping.
On the other hand: If a magus tailored a circular ward to warp people as much as possible, himself excluded?
Sounds good as a protection for a sanctum 
I will respectully admit that this is a YVMV sort of thing. Keep in mind though that I come from an older version of the game where there were far fewer sources of it. I like the Warping system better than the old Twilight points scale, but I myself tend to hand wave over continuous effects other than Longevity Rituals. I mean, I keep it in mind, I just make it really easy to fudge past. The reason being is that, for my style of play, I think Warping is accumulated too quickly.
So I think it is a fair criticism, just one I know not everyone agrees with.
I think it depends how you see a circular ward. I see them as only having effect at the boundary, not within. If somebody decides to summon a demon within your circular ward against demon you're SOL (though it has to cross the ward to go destroy the rest of the covenant). It is recommended to use a spell ridding an area of vermin before erecting a ward against them or you'll only keep them in...
Yes this is different from how an Aegis works but according to the RAW an Aegis is special (and we have references of containing summoned creatures within a circle in the rules...).
Stephen
And we're back to the question of whether living in a Shrouded Glen warps the inhabitants or only the glen itself.