Discussion of House Rules and Character Development questions go here.
Great! Excited! Fun!
I'm still not sure when the bp are spent. During post gauntlet character creation? Or at the very end (like mustering out in Traveller)?
I've also wondered: Are we all magi newly arrived at the Scandinavian covenant location or have some of the magi been there for decades. Will we start with an existing covenant or is our first spell going to be a round of summon a nice tower?
Another question: Which and how many languages does a Raven of Virtue speak?
Or I could just take the wise Owl of the Forest because she speaks all languages?
Ther raven is more stylish. Maybe I could give him an extra virtue by having him practice it for two seasons (and spend 2 x 2p of vis to make learning possible)
This is kind of important because my character will be mute.
Both. You'll need some vis during development, because you'll want a longevity ritual, and in your specific case, you want a familiar. So, you'll need vis for sure. Any build points you don't use, you'll muster out with.
I can't quite suspend my disbelief to the point that there is a covenant extant in Scandinavia that you would be joining. So, I envision this being some sort of assemblage of magi coming together to flee the Order. Redcaps are still delivering mail, so there can be ample discussion between magi. We can come up with how everyone was assembled, if it's really important. Whether you have a tower is dependent upon whether you have someone who can cast it and knows it... And then I'm sure that there are abandoned buildings, or buildings whose owners could be evicted...
So, I don't see anything suggesting the Raven of Virtue knows more languages. All familiars know the same languages their magus knows, learning them when bound. I don't see why you can't add a Quality granting Gift of Tongues to a Raven, though. A talking Raven is probably draw some comparisons to Odin, though.
Character gen question: if we decide to utilise the House mystery options, we should expend a season per initiation?
Question to the other players: is anyone pondering a Necromancy, Herbam specialist, or Ice Wizard themes?
Still need to do some reading before I choose a theme and story elements, so want to rule any out early if somebody else has a hankering for them.
Yes initiating a mystery also takes a season. Certain scripts require sacrifice so we will work out specifics in the character thread.
Do characters start their pg time with a lab?
I am planning on making a gentle gifted maga, a former Princess, so some social abilities and Mentem - haven't decided on house (I am loathe to do the obvious and choose Jerbiton). Maybe I will also have some Imaginem, for protective illusions - especially since we prob. don't want other magi to just waltz in.
There are ruins dotting Scandinavia from wars and rebellious hirdsmen (lower nobility), maybe an old viking village with many rituals have a Magic Aura, was abandoned and later a hirdsman built a manor there. Lots of possibilities. Regarding covenfolk, is it fair to assume that each magus/maga brings a handful ?
I need to read the advancement rules carefully so I don't make mistakes 
Yeah, I think it's not too unreasonable to allow a basic, standard lab. You can also improve the lab and move it to the new location. Doing so will cost some small number of build points that must be converted into silver to pay the additional upkeep costs. Of course, you must also pay the relocation costs from your build points, too.
Does the following mesh with your plans, Jonathan.Link?
My character's parens was one of the first magus affected by the malady, and before the parens cut off correspondence, my character's impression was that he was working on a cure. The parens lost his Gift and left with his stuff before publishing anything. My magus has broken into his old lab and found hints that he went to Sweden. Hence the hope to recover these attempts and learn from them, and hopefully at some point invite the disempowered magus to the protection of our newly founded covenant.
I'm playing with the idea of a Bonisagus who is a member of the Colens and is attempting to rouse his House to a response, asking other magi to also trace the belongings of disempowered magi and share them, to help with studying the disease. His intuition is that many of the infected must have worked towards a cure like his parens, and he hopes that studying their texts is safer than engaging an infected person directly.
Wits, that's fine.
Is it ok to design spells for initial character creation?
It appropriate for the magus at gauntlet, but yes. Designing spells is part of labwork, so take seasons away from advancement.
Can I play a Tremere who has taken advantage of the situation to loot Lycaneon of magical goodies but has had to spend a bit along the way? He'd need to be an OK age to get the BPs needed, use the 10% of BP allowed as vis to buy a longevity ritual, familiar, enchant his talisman and make a couple of useful items, a few on books, some on gold/silver from the immense Tremere reserves and most on magical items.
How old are you thinking? I'm reluctant to make exceptions to the vis limitation. The system was designed to mimic the tradeoffs characters often have to make in play. LR or talisman or familiar, which do I choose? There's also the premise that the line suggests in Guardians of the Forest and I subscribe, that it takes about 30 years to get all three that are decent. LR 14 (25 pawns of vis) is good, it'll last most characters a long time, might even be the best some characters get. 25 pawns for a talisman, is pretty great. 25 pawns is a heckuva lot for a familiar. 30 years isn't even that old, Hermetically speaking.
One of the hidden features of this system is that BPs can be used to buy items, and I don't care if you claim your character made them or not; if you claim that they were made by your character. If you spend BPs on items that you make, there's a side effect that you don't have to spend seasons in labwork, and get XP.
Of all the Houses I think Tremere would handle this plague the best. At the minimum I would think that they shutdown the borders to Transylvania and allow no one in or out until they are ready. My guess is that the Tremere outside of Transylvania are basically on their own. No or limited House resources.
It brings to mind another House that would be transformed. Mercere could have an interesting time. How many Covenants would refuse to allow entrance to a Redcap when they fear the plague? Perhaps kill the messengers? Would this collapse the vis trade? It would certainly limit the knowledge that moves through the Order.
Some advice needed 
What house do you think could be interested to add to the mix? I have really thought about my house, but no one house springs forth. I think it would be valuable to have a Quaesitor/Guernicus to advice on legal matters and give a veneer of justifiability to our actions. At the same time, a Gifted Mercere would be interested, also for the reasons mentioned before - the killing og travelling redcaps, vis trade breaking down etc. Having a maga having this as a problem and trying to rectify it in Scandinavia is interesting to. Then there is a Trianomae, political, alliance seeking, trying to bring about cooperation for the greater good - but that one doesn't seem as interesting to be honest.
Ideas?
I will admit that I am considering a Gifted Mercere for the reasons listed. It would be interesting to plump out the stories from the House and the Plague.
I will also team up with anyone who wants to be a Tremere. I think they would gather for support if cutoff from Transylvania. Perhaps ordered to build a outside Covenant for regrouping and supplies.
I hadn't looked at characters too much, was doing that this morning, and what you wrote out screams Jerbiton, especially one of the leagues mentioned in Houses of Hermes:Societates, but I can' recall the name of it, and I'm transitioning to a new computer, and my books are still downloading...
If there's enough of a demand from the players to have a veneer of legality to their actions, I can bring in a Quaestior as an SG character.
Jebrick and ROF, Please tell me as soon as you know whether you'll go for a Mercere and whether you want the Mutantes virtues if you do. I was considering either a Bonisagus with some Mutantes virtues or a Mercere with Tamed Magic, but I'm defaulting to avoiding those since both of you expressed interest in that direction and it is not necessary to my character. But if no one else does it, I might add them later.
In any case, I'd like him to lean towards MuCo.