Quick post to seek an opinion from the boards. I'm drafting a Vim specialist and pondering types of focuses that the Magus could have as Vim is a little too broad a flavour for what I have in mind.
I was thinking of a minor magical focus in Arcane Connections, so that effects (enchants, spells, etc) which use them are enhanced. I think it is narrow enough for a Minor vs being a Major focus.
As I pondered the idea I got to thinking about having foci in spell ranges, durations, and targets in general might be a very handy focus. So handy that it might need to be a Major focus after all. i.e. All spells cast at Voice.
I'll agree with that - Arcane Connection is certainly specific enough to be minor, but something like Sight would likely be Major - if not outright diallowed, due to being too broad. (IMO, at least.)
Although from a Game Mechanic standpoint, ReVi's Intangible Tunnel is functionally this: a spell that adds Arcane Connection to any spell you have. So there are ways of, if not duplicating, then at least getting very close to, this ability. For example: a minor focus in ReVi, and spending a season investing that power into a lesser enchanted item. Maintain the Demanding Spell grants a similar effect to Duration. Thus, you may find that such a minor focus ends up being overshadowed by 2 relatively easy-to-learn-or-put-into-your-talisman effects.
I for one wouldn't allow it as anything less than Major, since it covers far more than just an aspect of a Technique-Form combination. But I probably wouldn't allow any instance of R/D/T to be used as a Focus to begin with.
Spells that affect ACs in some manner, sure. The CrVi and PeVi guidelines that lengthen and shorten the duration would be a minor focus, as an example. A bonus for any spell at R:Arc, definitely not (as said elsewhere). A focus in any range is well beyond the scope of a focus, as it could be conceivably used for every single spell in all TeFo combinations.
...and could be replaced by a single Intangible tunnel effect. That's mainly my point, I guess: in terms of game balance, at least, having an "AC range" focus has less ability to modify the game world about it than a ReVi focus....which allows you to both increase the range, increase the duration, delay the spell, cast wards, cast the Aegis, AND gain increased penetration (technically - with the Suppress Magic effect).
(And yes, I know it's technically "slightly less than a FoTe" for a minor focus. I've found it to be convenient to just call it a FoTe. If someone feels the need to be technical, feel free to throw out the Render the Magical Beast power.)
I'm trying to think of scenarios in which you would want to use an AC range in which you wouldn't want to use an intangible tunnel....
When you literally don't have the 1 round it takes to cast the intangible tunnel before you start needing to get the spell off. (extremely unlikely)
When your target has defenses vs. Intangible Tunnel (slightly more likely - Wizard's war scenario)
So I guess it's that last one: if the character has specialized in a few low-level spells (such as that heat sink one, or a touch-based flame attack) that are jacked up +3 levels to cast them at AC range rather than through an Intangible Tunnel, yes. It would work better at getting through the target's Aegis+Parma than an Intangible tunnel would get through Aegis+Parma+Antimagic(vs. Tunnel). And THAT sounds like a minor focus to me.
For someone who wants to take it? Eh, I'd say let them. For 99% of the reasonable scenarios, they're going to be spending a LOT of time learning a bunch of different +4 magnitude spells for not a lot of benefit. For the one time it is useful, I will let them have their time in the sun.
I assume you're talking about using a normal spell, but because you have an arcane connection to the target, you can use it to boost penetration.
If you're including that in "minor focus: AC", then yes. I agree - that is too broad to be a minor focus. As stated previously, I was addressing having the "Range: AC" as the focus only.
Yes. This is the implied scenario on the 2nd point - that the individual you are casting at has some sort of defense against an Intangible Tunnel. (Although admittedly I only explicitly mentioned Parma+Aegis+antimagic). In this scenario - sure. But if this is the case, then your actual minor focus ends up being is "highly optimized lvl 5+arcane connection spells in your specialty." Because that's all you're going to be able to get through someone's Parma+Aegis.
OK - so you've got a 15Te +15Fo +15 Focus +5 miscellany = 50 casting total. An AC spell will have a minimum level of 25 (base 5 +4 mags), which leaves 25 +stress die penetration. Assuming 20 levels of parma and a lvl 20 Aegis, you're going to have to roll a 15+ on that die.
Of course there are ways to improve that number - you've got an AC, so you can get better AC bonuses. But the point is: that scenario right there is pretty "minor", in my book: the PC has to invent a bunch of inefficient, lvl 25 wizard war spells in their own specialty, and then use them only for that task. Which, IMO, is a highly-inefficient way of waging a Wizard's War - the only real benefit seems to be the element of surprise (no Tunnel), at the cost of everything taking 3 magnitudes more to learn, and not being particularly useful afterwards.
I'd disallow it (as intended by OP) more for an "aesthetic" principle than anything else.
It seems to me that all examples of focus are about the "object", rather than the "parameters" of your magic. So you can have a focus in lightning, necromancy, vermin, and even damage or parenthood; but not in non-fatiguing spontaneous magic, mastered formulaic spells, or R: Arcane connection (unless it's a Vim focus that only allows you to target that type of magic with your own metamagic).
A focus in Arcane Connections would then affect the detection, destruction etc. of Arcane connections (and could possibly cover metamagic affecting R:Arc effects); but it would not cover every magical effect with R:Arc. Even then, it would be somewhat tricky to adjudicate, since alot* of stuff is an arcane connection to something else.
Certainly, I agree that tunnels are a good way to wage Wizard War if you have an Arcane Connection to the target, and want to wage the war remotely. Although it still doesn't work if you don't have a good enough ReVi Casting Total. Take Darius (ArM5, page 34-35). He has a PeCo Casting Total of 36 and a ReVi Casting Total of only 17. He's at about the break point where he might be better off not bothering with a tunnel, particularly as his Penetration specialisation is Perdo.
Although, if he has an Arcane Connection to a Wizard War target, Darius' best option is probably to use that Arcane Connection to cast a Leap of Homecoming to teleport to the target's location and then stab the target with his spear.
Killing a Magus with mundane means is one of the best ways to do it. Unless that Magus is physically boosted to resist damage and all sorts of mundane attacks a spear, dagger, arrow, etc are often very effective. The old concentration based long drop pit is a good one too.