Let's suppose I want to poison someone who has at least some degree of magic resistance (whether that's due to being a magus, or from divine protection - most kings will have magic resistance, after all).
I want to use an ingestive poison, and I want it to have a decent chance of doing something useful. Going to a lot of effort to give someone a medium wound is not going to achieve much in most circumstances - I want Fatal or at least Incapacitating. The target also needs to fail their Stamina roll against the poison - assuming they have confidence points and a moderate stamina, that implies an EF of a minimum of 9, and preferably at least 12.
Let's say I try for an Ease Factor 12 poison that does an Incapacitating Wound. How can I build a character to achieve that (preferably that isn't hyper-focussed on it)?
For a Hermetic maga, I could do it as a CrAq ritual. Base 20 + 1 Touch + 3 EF = 40 for a single dose of poison. That's extremely expensive, but it's fairly doable, and gets more efficient if I up it to Group.
If I'm not a maga, the other two ways to potentially do it that I can see are Mythic Herbalism, and using the Theriac rules in Art & Academe.
Using Mythic Herbalism, it's EF 15 to create a poison doing a Incapacticating Wound with EF9 to resist, so say EF 18 for EF 12. So I have to beat EF 18 with Mythic Herbalism + Int +die. With an Int of +3, that means I need a Mythic Herbalism score of at least 10 if I want a decent chance of success - that's pretty high, but not undoable. However, it's not clear whether Mythic Herbalism circumvents magic resistance - it is a Supernatural ability, and unlike Mythic Alchemy I can't see that it explicitly says the result is non-magical.
Using Theriacs, you need a Formula of Base 10 + 4 Mighty =30, against a Lab Total of Int + Medicine + Max(Medicine) in Philosophic Bonuses. That's extremely hard. Assuming an Int of +3 again, and that you can max out your Philosophic Bonuses, you need a 14 in Medicine to create it - not exactly a low score, even allowing for a speciality and Puissant to bring the effective level down to 11.
Should the creation of Mythic Herbalism be magically resisted? Is there a way of making poisons in an easier fashion / adding bonuses that I've missed?
It feels like creating deadly poisons should be easier than this - yes it's a skilled job (especially if you're trying not to kill yourself in the process), but you shouldn't need to be in your late forties to achieve it. I don't know if part of the reason for it is a feeling that having your character murdered by poison is pretty much never going to make a player happy?