Can a magus wielding a +1 Defending weapon add an additional +1 enhancement bonus to said weapon using his arcane pool and then transfer that weapon's now +2 enhancement bonus to his AC?
Can a magus wielding a +1 Defending weapon add an additional +1 enhancement bonus to said weapon using his arcane pool and then transfer that weapon's now +2 enhancement bonus to his AC?
Pretty much.
Defending: "A defending weapon allows the wielder to transfer some or all of the weapon's enhancement bonus to his AC as a bonus that stacks with all others. As a free action, the wielder chooses how to allocate the weapon's enhancement bonus at the start of his turn before using the weapon, and the bonus to AC lasts until his next turn."
Arcane Pool (Su): "At 1st level, a magus can expend 1 point from his arcane pool as a swift action to grant any weapon he is holding a +1 enhancement bonus for 1 minute."
So once you've used your swift action to grant your weapon an additional +1 enhancement bonus, then at the beginning of your next turn you could use a free action to allocate any or all of the (now +2) enhancement bonus into AC.
What about a Staff Magus, who gets added AC equal to the enhancement bonus? Does he get less added AC when he shifts the ehanncement into defense? (netting no benefit) Or does he get AC equal to the weapon's base (and Arcane-boosted) enhancement bonus, and then still be able to use that enhancement for defense? (netting possibly twice the AC boost)
So once you've used your swift action to grant your weapon an additional +1 enhancement bonus, then at the beginning of your next turn you could use a free action to allocate any or all of the (now +2) enhancement bonus into AC.
Could you not perform both the swift action (to imbue the weapon with additional enhancement bonuses) and the free action (to transfer those bonuses to AC) during the same round?
What about a Staff Magus, who gets added AC equal to the enhancement bonus? Does he get less added AC when he shifts the ehanncement into defense? (netting no benefit) Or does he get AC equal to the weapon's base (and Arcane-boosted) enhancement bonus, and then still be able to use that enhancement for defense? (netting possibly twice the AC boost)
Quarterstaff Defense (Ex): "At 7th level, while wielding a quarterstaff, the staff magus gains a shield bonus to his Armor Class equal to the enhancement bonus of the quarterstaff, including any enhancement bonus on that staff from his arcane pool class feature. At 13th level, this bonus increases by +3. This ability replaces the medium armor and heavy armor class abilities."
If you have a +1 defending quarterstaff, you're getting +1 shield bonus to AC. If you activate the defending property at the start of your turn, you're now effectively wielding a +0 defending quarterstaff, getting no shield bonus to AC, but instead getting a +1 bonus that stacks with everything.
If you spend an arcane pool point to make it a +3 quaterstaff, you're getting a +3 shield bonus to AC. If you activate the defending property at the start of your turn, you're now effectively wielding a +0 defending quarterstaff, getting no shield bonus to AC, but instead getting a +3 bonus that stacks with everything.
If you used Defending first, (+0 shield, +1 stacks) then used the pool, you would end up with +2 shield, +1 stacking until your next turn, when you could choose to have +3 shield +0 stack, or +0 shield +3 stack.
Could you not perform both the swift action (to imbue the weapon with additional enhancement bonuses) and the free action (to transfer those bonuses to AC) during the same round?
Yes, but the order matters. Defending must be activated at the start of your turn. If you've used a swift action to activate your arcane pool, it's no longer the start of your turn.
One could argue that "at the start of his turn before using the weapon" is intended to mean "any time during his turn as long as he has not yet used the weapon, but intends to" or something, but that's kind of weird.
