I'd like to take the opportunity to crowdsource more interesting ideas what would happen to the Rhine Tribunal, to the Order and various houses if Durenmar falls.
In my current campaign, one thing led to another for many years and the very old dark faerie plot of vengeance at Durenmar (involving the black Fir) has finally come to fruition. (Interested parties can follow it here in #99, in full 500+ page Chronicle posted here: Ars Magica: The Rhineland Chronicle of Collem Leonis )
It's complicated, but in essence and related to some character choices, the dark faeries have subverted the aegis and aura for a long time, and they managed to subvert it to faerie being against the magi (i.e. really difficult casting spells) and invade with hundreds och bochmen and other fae creatures.
This happens at the final night of the Rhine Tribunal (year before the Grand Tribunal)
About 1/3 of Rhine magi have left the tribunal before this happens. Crintera and all Bjornaer have already left (for campaign reasons) and aren't affected at all (but unable/unwilling to help defend), neither are Irencillia (some left, others have passage or know enough about faeries to avoid).
Many magi - but mostly the younger ones are slain, while 1/3 of the magi scatters into forest or manage to get off a Leap of Homecoming or teleport despite negative aegis. Maybe 1/6 of Rhine magi and nearly all Durenmar magi take up defense in the towers while the faeries are in the process of cleaning out (or capturing) the rest. That's pretty much where we are in the game.
Most likely, due to earlier interaction and peace-brokering the dark queen will allow the player magi free passage out (to have potential political repercussions later with the Order), and quite likely will manage to fold the entire site into a regio so Durenmar disappears and will be incredibly hard to find again. The Durenmar elders including Prima Murion, the great library etc still being intact but trapped (something we'll investigate if they manage to break out or players take any action... from diplomacy, to violence, to subterfuge etc.)
[Note: I don't quite run my faeries as Ars Magica raw - they are less predictable, more aware, mysterious, powerful with more might, and are definitely scary.]
Now I think a lot about how this will affect the Order, the Tribunals, Houses and various factions and how they will each react (if at all). Certainly there is immense opportunity for fun sessions investigating all of that. It bears to say that wilderists, most Bjornaer, Merinita and some others have been critical of Durenmar and prominent Rhine magi not fulfilling their oaths as "Guardians of the Forest" and this may be argued as repercussions because the code was broken in the past (don't molest the faeries).
Also in my campaign, the players found out that Durenmar - as well as their own covenant - is built on devastated faerie sites - the old dark queens castle in Durenmar's case, so lot's of old grudges here.
The politics of Rhine is also split by Lotharingian tribunal schemes being uncovered, and likely voted on next year at Grand Tribunal (and where will the Grand Tribunal be held? Lot's of fighting about that for sure).
A delightful mess unless the players somehow turns things around next session (cheeky bastards have managed that a few times).
What do you think? I'd love a ton of ideas how various factions could react and what they'd say.
For sure there would be some rescue attempts - or attempted vengeance - while others laugh at the misfortune. Wild scheming would probably start across all of Europe, and many should see it as opportunity to take action in some way.