Divine defiance from fiendish codex 2

[calighis]

could someone please tell me how that feat works?
Can I counter arcane spells with it?

 

[TessarrianDM]

I would say that you can. Unlike the Divine Metamagic and Divine Spell Power feats (from Complete Divine), Divine Defiance does not specify anywhere in the text that it applies only to divine spells. The only stipulations it has are that you must have the same spell memorized as the one you are trying to counter, or the Dispel Magic spell. Counterspelling with the same spell does not require you be the same type of caster (a divine version of Hold Person will counter an arcane version of the same spell, for example). I would even say that if you have the Improved Counterspell feat (Player's Handbook) that you could use it in conjunction with Divine Defiance.

Of course, in all cases, you must have a use of Turn or Rebuke Undead available to power this feat.