...specifically, what's canon on them. In context, I've signed up to do a story line in my current campaign for a Bjorner player - he's got the Enemies (Shapeshifter) story flaw. It really hasn't been defined any more than that, so it's really up to me to decide what goes on here. OK, fine. The covenant is set in the Rhine, and so far I've got the following information, based out of HoH:MC and GotF:
Bjorner really don't like other kinds of shapeshifting - it runs counter their practice of revering ancestors as spiritual animals. (aka "the heartbeast thing.")
Bjorner don't go after other Hermetic magi that much (considering them to simply be ignorant/misinformed), and they pity lycanthropes, but they REALLY don't care for the Gothic Witches of Pomerania, as they consider the practice of commanding animal spirits to be evil/nasty/wrong. The Witches are the cult that Bria left to join the Order, and so there's some bad blood there on both sides of the equation.
Most hermetic magi really don't know much about what goes on amongst the Bjorner, and as such they tend to think of the group as "those pagan Germanic shapeshifter magi" (Even though they're not, really), although they've got a good relationship with Merinitia, and they were neutral/pro-Diende during the Schism war.
The Gothic Witches don't actually exist (Charlemagne wiped them out) - the only group of shapeshifters in the Black Forest are the Werewolves of Pomerania, who are only organized in the loosest of terms. However, these folks are the inheritors of the Gothic tradition, and they really don't care for Bajorner magi.
In the core rulebook, you've got Shapeshifters (who can do multiple shapes), Skinchangers (who can do one shape), and Lycanthropes (who can do one shape, but it's uncontrolled.) The Werewolves of Pomerania tend to have all three, depending on gender and how they were raised. None of these types of shapeshifters have infectious bites.
OK - that's pretty much all that I've found (are there Infernal, infectious/cursed-type werewolves? I thought there were, but I can't seem to find any). Is there anything else?
You can give creatures whatever powers you want. In terms of infectious infernal werewolves, here is an idea: When you get infected by one it doesn't take instantly, but gets triggered the first time you commit a mortal sin. Bam! You're a demon and can longer repent. (This general idea works for infernists and other demons too. As soon as someone damns themselves drop mind control. Then you get the soul without worries about repentance AND get them to work in the mortal world. That could even be a way of enforcing demonic "contracts". You're mind is controlled so you can't repent.)
As it stands, there's not a whole lot of canonical information about the Pomeranian witches apart from the aforementioned sections of GotF & HoH: MC so you'll have to fill in the blank spaces yourself.
The most interesting aspect from my perspective is Birna's assertion that they were 'soulstealers' and what exactly this might mean. Some of my personal favourites takes on Birna's this aspect of the Bjornaer founder's parent tradition are that:
They were a variant form of Folk Witch who employed something similar to Ars Goetia or Ars Fabulosa to control spirits. This may not necessarily have had anything to do with their shapechanging, however.
They were a type of Spirit Votary with ties to their tribal ancestors, but perhaps ones with few scruples about using up their patrons' Might scores or even destroying them altogether by reckless usage of Ritual powers.
Birna was wrong. Her tradition possessed an initiation script for Shapechanger and made extensive use of Magic Lore to created Enriched Items of Virtue which she interpreted as enslaving her ancestors.
They were a type of Taltos/Shaman, but perhaps coming from a tradition that taught Shapeshifter as well as having animal themed phantasticum (Birna was new to her tradition and not necessarily well versed in its lore).
As for infernal shapeshifters, the Damhadh Duidsan fit the bill as does any tradition with access to Debauchery/Phantasm. If you want to create the infectious type of lycanthrope (which I believe is anachronistic in ME), I suggest giving the beast access to the "Grant Flaw (Lycanthrope)" power it's pretty straight forward and the necessity of biting the opponent not only lowers range to Touch, but has the added benefit of providing the creature a handy Penetration bonus!
Not canonical, but my first article I ever wrote for Ars Magica (ArM4) in Hermes Portal was about this tradition. Back in ArM4 Bjornaer were more about shapeshifting, so I used some of the concepts from Erik Dahl's "Bjornaer Mysteries" article from Hermes Portal #2 to complement the basic shapeshifting. I've lost the original copy of the manuscript sadly, but always wondered if I should go back and update it - some of the ArM5 Bjornaer Mysteries would be appropriate and perhaps some of the Nature Magic Mysteries also.
yeah, my original thought, after reading through all the available material, was the Folk Witch/Ars Geotia combo.
I like to stick as close to canon (except when there is reason not to), so my thought is that there's someone running around, trying to re-create the magic of the Gothic Witches, and ends up getting the Bjorner stirred up thinking that their "ancient enemy" has come back to light. But no, it's just this 200+ year old Russian hedge witch doing the equivalent of Magical Breakthrough research, and getting a tribe of Pomeranian werewolves that she's been "studying" stirred up as a consequence - which freaks out the Bjorner, which concerns the Quaseators, which piques the interest of Tremere, etc.
(In fact, the Werewolves are just trying to collect enough vis to power some effects to MAKE HER GO AWAY. Either that, or bribe her to go "study" a different tribe.)