PFSRD:Greater Magic Fang
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Magic Fang, Greater
School transmutation; Level druid 3, ranger 3
Range close (25 ft. + 5 ft./2 levels)
Target one living creature
Duration 1 hour/level
This spell functions like magic fang, except that the enhancement bonus on attack and damage rolls is +1 per four caster levels (maximum +5). This bonus does not allow a natural weapon or unarmed strike to bypass damage reduction aside from magic.
Alternatively, you may imbue all of the creature's natural weapons with a +1 enhancement bonus (regardless of your caster level).
Greater magic fang can be made permanent with a permanency spell.