Wood that has been struck by lightning has a Shape & Material bonus, which leads me to the question:
How do you adjudicate whether a player can acquire something like that?
I'm asking in general--how do you decide if a player has a tough or easy time acquiring various unusual materials, especially if you're not building a story around it? (Argentius provides a system for that; it focuses entirely on trade within the Order, but I'm thinking more widely.)
And I'm also asking specifically about lightning-struck wood. Can a Magus who knows Incantation of Lightning blast a tree to acquire some? (Would that Magus be able to easily sell or barter off the chunks to other Magi?) If using IoL seems too cheesy, can a Magus or Storm Wizard create a thunderstorm and hope a tree or two gets struck? Or does it have to happen entirely independent of magic?
You just make something up that seems reasonable. Either straight out decide that they can/cannot find the material with relative ease, or make up a percent chance and roll the dice.
I don't think it would be possible to create a general method for determining such things that give good results and doesn't consist of a gazillion table of everything you can think of (except of course whatever the players decide to go look for...)
We had a magus experimenting with "Wood struck by lightning".
Does it still work if it's natural lightning, but targetting is controlled via Rego?
Does it still work if you simply cast Incantation of Lightning at a tree? Does it change anything if you're flying above the tree while casting that IoL? etc.
Troupe negotiation! In general, most unusual but mundane materials should be well within the means of the "average" covenant, particularly if a magus can wait for a few seasons to tap the local contacts, the Redcap network, etc.
Of course, if the troupe has taken some specific Hook like Poverty, they have already made it explicit that they'll have stories about such stuff.
Sure. Or a magus specializing in bees can send out a swarm to hunt for such a piece. Or a folk witch grog can dowse for one. Etc.
And each of these means has the potential to generate a story. The incantation of Lightning might start a fire. The bees might cause trouble with the locals. The witch might get kidnapped. Etc.
I think there's three main avenues for acquiring the trickier stuff:
1.) Redcaps (they have a logistics network and can acquire stuff).
2.) Tribunals and fairs for trading magical stuff
3.) Mercantilely oriented magi (often Jerbitons) who deal in such things
Keep in mind as well that availability will vary by location. Live near a forest? Lightning struck wood is probably fairly common- especially if the average peasant forester knows there is any kind of premium price for it (even an extra copper for a small piece makes it worth picking up). Scarcity is relative, something most RPGs don't reflect with their price lists and standard acquisition rules.
"The wizards will grant you a dear wish in trade for lightning-marked wood, perhaps even a bolt of good cotton!"
Research indicates that the Balkans and Alps have a relatively high number of lightning strikes, so maybe there is a small trade from that area. Woe to he who cheats.
That's how we did it in our game. My mage botched an incantation of lightning as we fought a magical beast close to the magical Birch tree that gave Ig vis, so the ST had the bolt hit and destroy the tree instead. So taking a branch of it seemed like a good talisman basis, even if Birch was not the must useful thing for a CrAu mage...