I'm wondering if there is any clarification regarding the rules for Opening the Arts to an Apprentice with multiple Supernatural Abilities and/or Virtues. Specifically, does the minimum Lab Total of 10 per Minor Supernatural Ability or 30 for a Major Supernatural Ability/Virtue go into the tally which must be exceeded? I.e. if one has a prospective Apprentice with Strong Faerie Blood and Shapeshifter, does that mean that the Lab Total has to exceed 140 for them to be presevered (30 for Strong Faerie Blood, 10 for the Second Sight included in it, 30 for the Shapeshifter, or 70 to Open the Arts at all, double that to preserve them)? I doubt if that's the case.
What I think is more likely is that the minimum Lab Total to preserve must be 60, or twice that for a Major Virtue. It must also be more than 5x the total of the two Supernatural Ability scores.
The answer is exactly what I was looking for. It seems flawed, however, since it is entirely possible to have a character with as many as three Major Supernatural Virtues of non-Hermetic origin. This would require a Lab Total of 180+ for the Magus to have been Opened to the Arts.
On a related point, how much control does a would-be Pater have in converting non-Hermetic Supernatural Abilities/Virtues to Hermetic Virtues? Preserving would mean that they stay the same. What does conversion do? Could one, for instance, turn Wilderness Sense into, say Free Study, or would it tend to come out as Inoffensive to Animals or maybe an Affinity in Auram, Animal, or Herbam"?
It's possible, but very rare. So if you want that, your parens was an Intellego Vim specialist, with an appropriate Focus, and all kinds of handy bonuses. Might just about be possible.
Alternatively, the character had two of them before Opening, and got the third by learning the Ability just after. Or there was a Mystery Initiation involved. There are ways around this, which I think is enough for a rare case.
Note that three Major Supernatural Virtues is generally a very, very bad choice for a magus. You'd get much more use out of a Major Hermetic Virtue and half a dozen Minor ones.
In-game, no control. It just converts. Out of game, players should get to choose.
Ah, thank you. You just confirmed one of my next questions, which was whether it was possible to have a Minor Magical Focus for Opening the Arts. It strikes me as an interesting possibility for a Bonisagus or perhaps Ex Miscellanea Maga. The former would be following in the Founder's footsteps by bringing those of exceptionally talented but difficult (in Hermetic terms) magic into the Order. The latter might be looking to establish a lineage of her own, or perhaps to perpetuate one.
Regarding conversion effects, it sounds like a worthwhile subject for original research.
The Lineage of Pralix, in HoH: Societates, has pretty much that concept. They have a Minor Focus in Exotic Magic, which would apply when trying to Open the Arts of someone already trained in a hedge magic tradition.