Provided that you find out which that is, before you have moved library, labs, kit and kin to it. Demons are subtle and had time to study you.
So better create 10 Aegides before you move?
This could become an adventure for young magi: they find a complete basic covenant with Aegis, buildings, laboratories and some unimportant books - but without any people. Later they also meet a little demon in it looking for company. 
That makes me curious about what kind of threats against your covenant you do want to play out, @Jetpack.
I am actually in agreement with Jetpack. Having started in and survived playing AM3, I don't enjoy the infernal. Their mechanics in AM5 make me dislike them even more, though I generally try to keep my dislike of them out of my posts. That dislike most likely amplified my response to demons showing up in my current game, since I amped up to the point where almost any demon shows up around me and it is destroyed in a round.
Sure, but the interesting question is then, what makes a good plot?
To me, the demon as tempters and as deceivers make good plots because they are subtle and expose personal moral dilemmas. This gives scope for RP. Combat plots become to straight-forward to my taste. Political plots are fun in theory, but I do not think I am able to manage their complexity.
The 3ed demon might well want to take over the covenant, but a 5ed demon, I take it, would go after the souls instead.
But yes, I can totally see a game without demons. I am just curious about different people's conception of `a good plot' ...
See the thing that you like about demons, I dislike. They force the story to move in a certain way, which might be a direction the players have no interest in. They are immune to detection and most spells. If the SG wishes it, they can force the game and the characters in any direction they desire with very little input or resistance possible by the players. In essence they reduce player control of their own characters and pass that control to the SG.
As for your question, here are a few plots and storylines that are on going in my Saga.
Landen Trading Company: Our primary source of income and a large driver of games. It has resulted in combat (pirates & pirate hunting mostly), politics (nobles, other traders, other magi), focused magical research & enchanting (including a magical shipyard), and a means to inject us into other locations and Tribunals far away from own. It is the reason several of our Magi have mental labs.
Pirates/Africa: Due to all of our ships found on the Med, we are constantly in conflict with the varies pirates found on the Med. This has actually resulted in quite a few adventures into Africa.
Regio Development/Hermetic Architecture: Our founder was a Boni researching Hermetic Architecture. There were a massive amount of planned and uncompleted ideas/features of manipulation of the Regio. When he went into FT, the Covenant inherited his notes. This has pulled us into adventures, role play, and politics trying to expand it. One of the players has taken up the founders research into "flavoring" an aura.
Covenant Development: Very closely aligned with the Regio Development, our Covenant was very basic at the beginning. We have spent a massive amount of game time finding and transplanting magical plants and animals to the Covenant. There has been lots of development based on character/player ideas. We have build a roman baths, a medicus, temple (see lower), and two resort/inns (one mundane, one in the Covenant). There is a ton of internal politics since the total population has broken 500 people inside the Regio/Covenant, in addition to all those in the Landen Village/Trading Co.
Book Exchange: From the initial minimal trading, we have developed a massive book production capacity. One of our Magus goes to not just our own Tribunal, but all of the surrounding Tribunal meetings. We tend to champion and support a great many young Covenants (Here, have some books to help you get started. Just remember us later). This pulls us into politics and conflicts in a third of the Order.
Magic School: While only a minor focus right now, we have been slowly building up from the traditional one-on-one apprenticeship formula of the Order. There are mundane teachers who teach the basics, a couple of Covenant held classroom labs where the Magi can spend a season of Covenant Service teaching all the apprentices as well as guest Magi teach (in exchange for books/access). This is going to result in some serious conflicts with the more traditional side of the Order.
Covenant Mystery Cult: Our Magi have been developing an internal Mystery Cult to integrate all of the disparate things we have been collecting from our research, adventures, and trading to fill in other areas of interest. The "God Learners" would be the closest system to describe our approach. It also causes lots of internal tension since half our Magi are Boni. How much of its developments must be shared, since they are mostly unusable without Cult Lore.
Tribunal Politics: We are in Provençal and near the Coenobium Rhodanien Covenant. Overall we think they are power grabbing assholes, who need to be split up into separate Covenants. They started off with a bunch of Chapter Houses and have only gotten worse. They also have been steadily trying to dominate the Tribunal and open ever more Chapter Houses.
Inter-Tribunal Politics: Our Covenant is located very close to the Provencal/Rome boarder. Part of the Normandy and Greater Alps Tribunals are not that far away. There is interaction with Thebes, Levant, and Transylvania (GRRRR Tremere) due to our location on the Med and fleet. We are involved in a great deal of inter-tribunal commerce (books, vis, items, services). We send someone to the Tribunal meeting of all of them except Transylvania.
Covenant - House Mercere Conflict/Politics: Coenobium Rhodanien is controlled by a Redcap (and we are in conflict with them due to Tribunal Politics). One of our Magus created a portal enchantment which freaked them out (they at first thought we stole the design of a Mercere Portal). We reached an agreement with them, which has resulted in a Mercere House on our island and a Mercere Magus allowed to join the Covenant. We also have two resident Redcaps (both Companions though), though they are strongly conflicted in loyalty between house and Covenant. We have free "non-commercial" access to the Mercere Portal network, in exchange for things like free Redcap passage on our ships, free access to our portals, creating a few of those portals for the House, and an Oath not to share/trade our Portals with others (no lab text or finished ones). We are pretty sure they are spying on us to the best of their ability.
Covenant - House Tremere Conflict: Several of the players (myself included) have a long standing dislike for House Tremere. Some of it dates back to older editions handling/design of the house, though even in the current edition they are still trying to dominate the Order and reshape it into their way of thinking. Our extreme aversion to dealing with them (notice we do not trade with Transylvania) has resulted conflict at times.
Cult of Hermes: The Mercere Magus who joined our Covenant is also a Priest of Hermes. We have built a Temple of Hermes in the Covenant. A portion of our Covenant was pagan and that portion has only grown larger since the Priest/Temple have occurred. We find and explore old Hermes Temples, with things found often being contested over between the two Cults.
Those are just the big things. In addition to these, there are a ton of character specific ones. We engage in Grog only adventures, apprentice adventures, and have even had a couple of games centered around the magic cats of the Covenant (three of them are familiars).
Thanks for the ideas. It is clear that much of that is of a complexity we cannot handle, at least not yet. One of the things I am wary of is the plots so complex that automatic successes are earned whenever there is insufficient time to RP the challenge. I am not saying it happens to you, but it would happen to me if I make too grand scale plots.
Now, it is the case that any powerful antagonist can force the PCs into a set direction. There is no need to overplay that power even in a demonic plot. I also know from the unfolding plot that the players keep finding surprising way to thwart the plot, and argue over which approach to take. But sure plots of temptation become very personal, and it does not suit everyone.
No single SG could handle everything our group is involved in without letting things drop. While we have a primary SG, everyone runs stories and so the load is split among 8 people. Additionally a lot of it is character driven, which frees up effort from whoever is being the SG for the current session.
We also do mostly troupe style play. All of us have our Magus, two Companions (or a single Mystic Companion), and varies personal Grogs. There are also a large pool of shared Grogs we can play. Things like familiars and important position Grogs tend to be personal (though the primary SG holds most of the Covenant Grog leadership), while most of the combat Grogs (outside of personal Shield Grogs) are pooled. If we primarily only played our Magi we would have to limit or cut out a great deal of things.
A lot depends on the type of demon- as a SG I tend to have demons be supportive of players- at least until they have gained the player's souls. Of course the way they are supportive leads to temptation and infernal paths- had one PC join an infernal cult in order to make his garden seem better. Of course the player knew it was infernal but the character managed to convince himself otherwise...
however that just involved correspondence with the cult leader rather than an invasion of the covenant. For me a demon which has invaded a covenant should probably be selling information about the magi to others, either to those who might corrupt the magi or to those who can be corrupted by trading for the information.
I am not so worried about the strain on me as SG, as I am on the strain on session time. Of course the complexity is also a cognitive strain, but a strain on me as player as well as on me as SG.
@silveroak has it right ... the advances these demons have made all play into goals and traits already declared by the players in advance. They tempt the characters rather than control them.
The problem we did run into though, is that roleplaying actual demon worship is tricky and unpleasant to some of us.
This will depend heavily on how (and if) the demons wish to be worshiped- not all demons want worship, some just want to corrupt your soul through other paths. Only the False Gods want to be worshiped, and even there a lot of variation can apply to how- perhaps the orgiastic fertility rituals will be something your players are okay with, or the sacrifice of animals (traditionally black). Modern day Satanists make use of illicit drugs in their rituals. You can in fact design an infernal tradition whose greatest discomfort is in how comfortable it is... after all demons want your soul, not your pain and suffering- okay they want both but they prefer your soul.
In our case there was a false god. And that is what was unpleasant. And no, there would not have helped to discuss it in advance, because nobody predicted their reaction in advance. This says nothing about the other demon encounters in the story, be they related or not to the false god. They seem to work thus far. The menace of resident demons is one which is yet to be properly assessed.
Quite logical, if magi were not up to the task when it appeared!
I can see we are very different on this point. I find it rather boring to focus on the long-term development following, more or less, a preset goal. It is the response to encounters and events that make the story worth telling for me.
Session Zero looks like Utopia from my point of view. Very few players are able and willing both to assert what they want to play and adapt according to a common vision. Some do, but they are the exception.
And it is difficult. Many do not want to assert their vision for the game, for fear of being to demanding or intimidating. Many do not want to spend a lot of time preparing because most sagas end quickly anyway. And quite frankly, we all have such widely different backgrounds so that we do not know what to ask to identify our differences.
I think much of the issues arising here are from differences in play style and preference. Some people like free-form play, while others rather structured. Some prefer character driven play, while others prefer SG driven play. Some rather goal oriented games, while others enjoy being completely side tracked. Some like combat/conflict focus, while others want to role play. Some like tiered/class advancement, while others rather open advancement.
Everyone who plays RPGs is somewhere in the range of each of those variable. Where you fall individually will determine the type of system and group you like to play with.
Myself for example:
Looking at my list, you can see why I like most of the WW games, AM, Traveler, and similar games. Though I have enjoyed games which are almost completely against my list while playing with people who have similar taste, such as Rifts. However that Rifts game would seem completely unfamiliar to those who play it in the normal beer and pretzels combat focused style.
I know that I would have difficulty in a game run by Loke due to his dislike of goal oriented play. Constantly being side tracked by "random encounters & events" is something I would quickly get sick of. There is nothing wrong with these differences, it just means that most likely we would not be a good match in a gaming group.
Sounds like you might need to come up with a questionnaire for your Session Zero. Asking about how much players like varies elements/flavor in games (on a say 0~5 scale, with the option of a hard "No" for sensitive areas).
You could also include things like questions on their thoughts on House Rules or Clarifications needed, both about specific things (Parma Magica, AotH, etc) and in general.
You can find varies examples if you google something like "Pre Campaign survey".
Funny enough, I would describe my preferences exactly as you describe yours. It is not correct that I dislike goal oriented play, although I do think that goals need to change along the way. Six players each determined to pursue the character goals they set ahead of the game is simply not going to make a coherent story.
My response was rather quickly typed, in that I notice I did combined individual character goals with group goals/development. The group goals are often what drives much "long term development", which you said you found boring (my mistake, I should have used your word rather than inserting dislike).
I actually enjoy that long term development, to an extent that I took part in a Cyberpunk 2020 game for nearly two years in which we actually started and built up a corporation as the main core of the game.
That enjoyment I have for long term development in games is what I felt would lead to any friction between us within a game.
EDIT: Sorry, it looks like I blew up your thread with post.
Actually, I was referring to character goals, not group goals. But the underlying premise here is that I have never managed to get a troupe to commit to shared goals. It is an online game. Too many players come and go. Some are somewhat less committed than others. Some show less initiative than others. I really would have liked to see more troupe goals, but I think you need either a troupe with some history together, or very assertive and pro-active players.
What I find boring is the uncontested development. I love the long-term development, but if everything goes according to plan, then it becomes boring. Therefore I do not mind being a sidetracked and turn into a demon hunter, if that is what the world demands. We agree that these encounters should not be random by the way. It is not random encounters that we are talking about.
A lot of the issues you are having is why I have avoided taking part in any online game. My longest group has been playing together for the better part of 30 years now, with many characters that have been around for 20+ years. It might be a year between a burst of games, but we know we can pick it up and have fun together any time.
In my AM game, my Magus did get sidetracked for a short time and became the "Demon Eraser". However sucking up less than 10 years of development in a fast paced saga with over 100 years is a minor distraction. It would have been a major distraction or complete character change in a slow paced saga. The speed and length of the Saga plays an important role into how detrimental side tracking is.
(If you are wondering, it is a WW WoD game, primarily V:tM though there is cross over. My Toreador Alex (that is Alexander Halthor the Third to you peasant) is still bumming around with his crazy Malkav friend Blaine. Even if the crazy b@st*rd still likes to hit him with garbage cans to help him train his Fortitude.)