My understanding is that a talisman isn't changed as the Bjornaer does. Which make talismans somewhat... less useful, very often.
For this reason, I strongly recommend allowing the "Inscription on the Soul" (described in The Mysteries Revised Edition) as a House Mystery for House Bjornaer. This allows them to enchant themselves as their talisman, thus keeping it with them even as they transform. I further recommend allowing them to Enchant the Body, and to have these enchantments retained into the heartbeast form. Having a Bjornaer magus with bones and stones and pieces of wood and whatnot sticking out of his body, in both his human and his bear (or whatever) form, strikes me as highly appropriate and cool.
Seriously, even when you are the storyguide, it is a good idea to discuss these things with the troupe (unless they are total newcomers to the game). Things like this are rerally minor restrictions or features, and have limited impact on the game.
In this case, RAW seems to indicate that the talisman does not transform by default (otherwise it would be noted in the talisman section on p.98), but a slight departure from RAW is sometimes a good thing to add flavour to your saga.
In the saga I mentioned, most of the player magi are shapeshifters of some sort and power level will be otherwise low, so I felt that this was a concession that would motivate them to create talismans they can easily travel with. This will keep annoyance about having to hide/transport their talisman to a minimum. And what the players have, the opponents will have as well. So if one of their antagonist is a shapechanger, they won't be able to object if he can do this as well.
I did. We decided to turn to the forums for input. Alas I'm here.
Actually RAW a Talisman does transform with the magus when using regular MuCo(An) magic, since additional requisites aren't required for it as it's considered part of the magus's body:
It just seems the Heartbeast is an exception to this, even though it's stated nowhere explicitely. I guess it makes sense given that the Heartbeast fits badly into Hermetic theory and actually is the magus's spirit turned flesh.
This sounds reasonable to me; because the Hearbeast isn't Hermetic you can't use casting requisites to bring "equipment" through the transformation. Potentially, an opportunity for a Bjornaer Mystery Script to allow this to happen?
Certainly, in my saga we have assumed that Bjornaer are liable to drop their talisman when they transform into heartbeast form. So Bjornaer tend either have talismans that both human and heartbeast forms may wear (necklaces, rings, earrings, etc), or have talismans that contain heartbeast-aware effects which do something appropriate when the Bjornaer shifts into heartbeast form (displace the talisman to somewhere safe, transform the talisman too, etc), or just don't have talismans.