I'm betting Thebes. Transylvania is too one-house-directed.
Yes, and then that is precisely what would make transilvania perfect for those that do not care at all about hermetic politics. You go OK with the tremeres and you get what you need from the tribunal. Goes well if your troupe does not enjoy hermetic politics. Some troupes don't, after all.
Cheers,
Xavi
Both Provencal and Hibernia were covered briefly. Hibernia listing all the covenants in the Tribunal back in the 1st edition Order of Hermes book and Provencal being the original Tribunal of use was covered in things like the original covenants book, the mistridge book and the 4 seasons adventure A Midsummer Night's Dream. Transylvania is not yet covered, but enough detail was given in HoH:TL that the Tribunal was completely under the domination of the Tremere to make it a boring setting.
Thebes is the Tribunal with the least official canon and the most scope to be made interesting, only a few covenants have been mentioned in 5th edition and then only in brief comments.
Only boring if you care about hermetic politics. If you don't give a crap about them, having an ubber-dominance can be a perfect setting to concentrat eon the "real things" in your campaign, like a strong story arc dealing with the supernatural.
Boring or not depends on your interests. Do not dismiss it so lightly 
Wat you consider boring others might cosnider to be a boon. Also, take in mind that "domination" and "lack of hermetic conflict or diversity" are 2 totally different things. 
As an example, the Stonehenge tribunal has been "dominated" as well for a really long time (by blackthorn), and that does not mean that things between covenants were peaceful, sedate and lacing in backstabbing.
IMO the transilvanian tribunal is really cool historically, as an european zone, so I would love to see a tribunal book on that area.
I and my group are setting up a Hibernian saga. It is true that the covenants of the tribunal are described in a supplement, but it is 2nd edition, totally lacks in any relationship with mundane politics (THAT is boring in our opinion ) and the covenants are naive to say the least. The description of the tribunal is not up to the current ars standard by a long shot. Other suppmenets (Lock Leglean, Rome and Iberia as well if you remove the demons...) have kept their value up to the challenge, but descriptions like that of the Hibernian tribunal are not up to it.
Cheers,
Xavi
Hey, I would love a book on Transylvania, but I just don't think it has enough of a broad appeal. A normal tribunal has a little bit of everything, and a bit of that will be missing from T., narrowing its target audience - which, let's face it, is small enough as it is. Atlas isn't in this buissness to lose money.
I think eventually a T. tribunal book would be on offer, as that fits the plans for the line, according to what we've been told, but I just think it's a low priority. It's better to cover more broadly-appealing tribunals, like I think Thebes is.
You know, I think this is perhaps the Tribunal with the most opportunity. Why would I say such a crazy thing? Well, read on...
Imagine House Tremere as an order unto itself. Imagine the Tribunal of Transylvania as a world unto itself. And start to look at the magi of Tremere as individuals within that world. Individuals all start from a philosophy of "them and us". And you can start at the highest level (the Order and mundanes, of the Order and other traditions). And you can break it down to House Tremere and the other Houses. But once you're in Tremere, how does that further break down?
Sure, outwardly they toe the party line, of course they do. That's the Tremere way. But behind closed doors, how does the House reach its decisions? Who opposes whom and why? What political factions dominate and how close to losing power are the current rulers? True Lineages provides the bare bones of this, but imagine those ideas presented to eager storyguides and players with ready-made antagonists ready to play out those roles and represent conflicting views.
Transylvania seems also to have been kept in a state of conflict, so there is story potential there. I wouldn't mind being filled in on the history of the area, its myths and legends, and the ways my magi from other Tribunals can be brought, logically, to Transylvanian lands.
Who are the twenty or so magi of other Houses who live within Transylvania? What brought them there? Why do they remain? Does "the House" have a direct hold over them? Are they not Tremere in all but name? How do they maintain their identity?
And with the House's current fascination with foreign traditions, you can imagine the Tribunal being filled with magi on the verge of "going native" being pulled into these strange other cultures.
There's a danger of the Tribunal book being Tremere-centric, but actually there's enough variation between individuals, and there can easily be enough rivalry and antipathy between covenants that the overal Tremere-ness is actually just a detail.
I have to say, this is a book I'd really like to see.
Good points all. My apologies for the quick dispariging of the possibilities. 
However, I would still point out that certain things that appeal to me at least would be missing. Take tribunals for example, the Tremere block vote principle if carried off ensure that any vote in the tribunal would be decided by the Primus Tremere as he orders his House to vote one way or the other. Politics internal to the house can of course occur, as can politics between covenants but whenever issues come up to be decided it's 'one man one vote' and he's the man with the one vote. The best stories internal to the Order, from my perspective, in the T. Tribunal are the border wars with other tribunals, on the western edge in the expansion of Venice into the balkans could bring Roman covenants with them, the Theban Tribunal has long backed the Byzantine Empire, wheras the Tremere back the Bulgars and their proxies are at war, the Tribunal of Novgorod is busy defending it's borders to the west and south from expansion from the Rhine and presumably from Transylvania too, but those are inter Tribunal stories. All I can say really is that my mental image of the Transylvanian Tribunal is one of order and strength as the Tremere cooperate and organize their Tribunal as their Primus dictates, and all members of the house and their pet experts obey.
There are plenty of other possible stories dealing with mundanes, with the fae and the infernal, and especially with the mongol invasion attempting to depopulate the Magyars for an old insult, but I like Hermetic intrigue and conflict, and that is hampered as stated above.
Nevertheless I'd buy the supplement if it came out, I just think the Theban tribunal would make a better choice for most players.
I'd buy either one of those two.
Tremere vote as a blocik in issues that concern THE HOUSE (and the Order, by extension), but 2 tremere covenaants can bicker A LOT as long as they do not kill any tremeres: that would reduce the voting weight of the Tremeres as a house and suppose a waste of wartime resources, and that is not to be permited. I cannot see the primus giving a yota about what happens over the conflict on a vis source, as long as the tremeres get it when they need it. And if the ones that bicker are 2 tremere-dominarted covenants it is totally irrelevcant who gets it.
I can see rivalries being as common bhetween transilvanian covenants as they are in the rest of the order. The fact that you present a united front externally doeas not mean that you cannot bicker internally. The OoH as a whole follows pretty much the same policy of you consider the externals to be anyone not in the OoH.
Cheers,
Xavi
The tribunal book I would most like to see is Thebes. In fact, after Lords of Men, it's the Ars Magica book I would most like to see.
There are so much in Greek myth that could be used in Ars Magica. Of course, being a film guy, I was really fired up by movies like 300 and the new trailer for the remake of Clash of the Titans. 
But the whole Greek myth... I think it would fit wonderfully with Ars Magica.
Cheers,
E.
If you're looking for a little taste of the Theban tribunal outside of HoH:S, Sub Rosa #4 has a description of a possible covenant set at the site of Seuthopolis in Bulgaria.
-Ben.
Good piece of work, too. I particularly liked the story seeds near the end of the article, one of which is quite topical given some of the content further up this thread.
Ben, this is really great work.
I think its in Transylvania, though...depends where the border is. I've always imagined the capital of the ancients to be the sort of thing tat Tremere would have grabbed with both mitts.
(Seriously...you should pitch for one of the open calls.)