At the start of your turn, you may declare that you are fighting defensively. If you do so, you take a -4 penalty on all attacks until the start of your next turn, in order to gain a +2 dodge bonus to AC until the start of your next turn.
If you use any offensive ability (any spell, spell-like, supernatural or extraordinary which either deals damage or inflicts a condition) that requires an action to use but does not require an attack roll, you must make a Maneuver Offense check, or a Caster Check (your choice), versus a DC of 10 + double your character's level, to use that ability.
This means using something like the Ifrit's Aura of Fire stance or the Bard's Harmony ability would require one of these rolls to use while fighting defensively. Only one Maneuver Offense check is ever required per action taken, even if multiple abilities occur during that action, and the Maneuver Offense check is ONLY necessary if no attack roll is being made during that action. Abilities which are free actions to use do not require a check. If the Maneuver Offense check is failed, you are still defensive, gaining the bonus to AC, but the action you attempted cannot be used this round, and the action required to attempt it is wasted. This is also true of spells — if you fail your Caster Check, you lose the spell, and the action used to cast it.
Fighting defensively can also be used in a round in which you make a full attack action, but must always be declared before the first attack of the full attack, and applies all bonuses and penalties to all actions made until the start of the character's next turn.
- Special: If you have at least 5 ranks of acrobatics, the dodge bonus to AC while fighting defensively is +3 instead of +2.