|Daniel Turner Zen Archer|
There's also the critical hit deck product which has some effects that can be drawn on any critical hits, even for magic. Some of the cards you can draw state that you deal double damage on your critical hit damage roll, which while not the same as a x3 roll, can equate to that. I'll look around for the product to see what the name of it is and I'll post it here later.
|Just a Guess|
You can deliver touch spells with natural attacks, but I do not know if that makes the spell crit as the natural attack does. If so take improved critical bite and polymorph into something witha x3 bite (I think there are monsters that have it.) . Else something with a 19-20x2
It does not borrow the multiplier.
I'd have to cross-check on the range, but that's nothing new-- Magi can be pulling off 15-20/x2 touch spells entirely under their own power by level 5, sooner with some decent gold.
The only way I know of is a feat from a pdf that contains many feats geared for the Magus (though not all require Magus class features.) One of which states that, when using Spell Strike to deliver a spell, if you roll a Nat 20 on the dice, the spell uses the weapon's crit multiplier. So that shocking grasp scythe may seem silly, but if that 20 comes up....
Yeah, it is a third party PDF. While I've always wanted to build a magus with that feat, I've never been able to bring myself to. It did have some other neat feats, like casting touch spells at the end of a charge (which meant you could Spell Strike), but some were a bit silly. I'd rather build my unarmed strike Magus idea. Not to derail the topic, though.
Well, to continue the derail: unarmed strike Magi are awesome. Use Hexcrafter, take Hex Strike, see if you can convince your GM to allow Hex Strike's stamina trick to pump your action economy a bit, punch out all the things.
I'll have to look into that option.... I was going to with the Extempresario archetype on the d20pfsrd to be spontaneous and charisma based (I know people say prepared is better, I've never been a fan personally.) That way I can take Eldritch Heritage at 3rd level to get the 3rd party giant bloodline (also on the pfsrd) to get a monks unarmed strike scaling. There are probably simpler/more efficient ways to build it, but I wont post my rough build here now.