Zone of Foul Flames

Transmutation
Level: Druid * 4, Hunter * 4
Components: V, S, M (a sliver of tree bark from a burnt tree from the Uskwood)
Casting Time: 1 Standard Action
Range: close (25 ft. + 5 ft./2 levels)
Area: 20-ft.-radius spread
Duration: 1 minute/level
Saving Throw: Will negates
Spell Resistance: yes
  The twisted druids of the Uskwood forsook fire in ages past for the glory of Zon-Kuthon. Despite this aversion, these servants of Nidal know well the sting of flame, and have learned to turn it back on those that wield it. This spell creates a zone where magical fire effects twist and lash out against those who create the effects. A zone of foul flames looks unremarkable to the casual observer, but a Perception check (DC = 20 + the caster's level) reveals a faint rippling effect in the area, as if of heat distortions in the air.
  Whenever a creature casts a spell with the fire descriptor or activates a magical fire effect (as from a magic item or a special attack) while that creature is located in a zone of foul flames, that creature takes full fire damage from the effect.
  If the effect allows a saving throw to reduce the damage, the victim may attempt the same saving throw to reduce the damage. All creatures in a zone of foul flames gain a +4 Circumstance Bonus on all saving throws against fire effects, except for those made by a creature attempting to save against fire damage from his own magic. Nonmagical fire in a zone of foul flames burns half as brightly but is otherwise not affected.