I'm looking at the Ex Miscellanea Virtue Craft Magic and an issue has come up. Can you use it with multiple Craft abilities, or are you limited to using it with a single Craft ability?
I note that the description of the Virtue states: "This Virtue has four applications, each described below. All of these rely upon the character’s skill with a particular craft, represented by a score in the Craft Ability or the Profession Ability." (Emphasis mine.) All of the examples refer to single-craft craftsmen. Could a magus take a half-dozen Craft abilities and use Craft Magic with all of them, or must he pick a single Craft ability for which he is trained in Craft Magic?
I don't think "a particular craft" restricts it. For example, the amount you charge for a job relates to your skill with that particular job. That doesn't mean you're restricted to a single possible type of job. However, I don't see any clarity in the description, though I certainly could have missed it. As far as I can tell it could be interpreted either way and not contradict what is written.
Personally, I'd allow several different Craft choices. I don't think it gives the Virtue that much more power since you end up sinking experience into multiple Craft Abilities, plus it's a Major Virtue and so you should get your investment out of it.
I had the same issue when last I reread the virtue (and the time before): RAW seems to refer to a single craft. But I don't think it is a very powerful major virtue, even if applied to all crafts.
As I understand HoH:S p.131, the Rusticanus for each time he crafts a spell or item with his Virtue Craft Magic needs to pick a single, particular Craft Ability. But he can pick different such Craft Abilities at different times, if he has more than one. If Craft Magic would only ever apply to a single Craft Ability, by ArM5 conventions this should have been recorded in its name, like Craft Magic (Blacksmith).
This just decouples Craft Magic somewhat from the campaign specific delimitations of one Craft Ability against another. So you do not need to dither, whether HoH:S p.130 Robert Wood had the Craft Abilities Bowyer and Fletcher, or a more generic Woodworking encompassing both and a lot more. Still, obtaining scores in several Craft Abilities that allow decent shape, material, design and inscription bonuses is a substantial investment of experience points, be that at character creation or later in the game.