A fury-born weapon draws power from the anger and frustration the wielder feels when battling foes that refuse to die. Each time the wielder damages an opponent with the weapon, its enhancement bonus increases by +1 when making attacks against that opponent (maximum total enhancement bonus of +5). This extra enhancement bonus goes away if the opponent dies, the wielder uses the weapon to attack a different creature, or 1 hour passes. Only melee weapons can have the fury-born ability.
So two different but related questions here:
1.) If I have both unarmed strikes and natural attacks, and a fury-born amulet of mighty fists, when I hit a foe with unarmed strikes, does it make the enhancement bonus of my natural attacks go up as well?
2.) If I have a +0 Furyborn amulet of might fists and have a +3 enhancement bonus on my unarmed strike (from Greater Magic Fang, say), will hitting with my unarmed strike make the enhancement bonus go up to +4?
prototype00
Better question why would anyone ever put Fury-born on anything? I mean give someone the choice of either a +3 weapon all the time or a +1 weapon that after two hits on the same target becomes +3, and maybe +4 or 5 if it takes that many hits to kill something.....and everyone I know will take the +3 weapon all the time.
Things just don't have that many hit points, if one of my PC's hits a monster 4 times it is either dead or on its last legs.
I think maybe as a +1 modifier it "might" be worth it for archers, monks, and two-weapon style melee types.
To answer questions...
1- yes anything the amulet modifies would go up since the amulet helps unarmed strikes and natural attacks both would get bonus.
2- no the bonus from the amulet would have to be better than that from the spell, you take the higher don't add together