"Each round on its turn, the subject may attemp a new saving throw to end the effect. This is a full-round action that does not proboke attacks of opportunity"
I take that as,
You cast the spell,(round 1)
Spell effects target (target get saving throw) (round 2)
(round 3)= target gets saving throw
(round 4)= target gets saving throw (passes saving throw)
(round 5)= target get to act normal.
|
Based on the language of the Feat and game balance, it should only apply to the initial application of the spell and not collateral effects that occur afterwards.
Benefit: Whenever a creature targeted by a persistent spell or within its area succeeds on its saving throw against the spell, it must make another saving throw against the effect. If a creature fails this second saving throw, it suffers the full effects of the spell, as if it had failed its first saving throw. A persistent spell uses up a spell slot two levels higher than the spell’s actual level. Spells that do not require a saving throw to resist or lessen the spell’s effect do not benefit from this feat.
It allows a 2nd shot at failing a save to suffer the "full effects" of the spell. Once the full effects are either implemented (e.g. paralyzed by hold person), or both saves made, the Feat has no more applicability. Any additional saves that would need to be made would be made normally as part of the spell effect that is now in place since you are no longer targeting this creature with the feat.
This feat does not make the continual spell effects tougher, just its ability to land in the first place. You could imagine the game imbalance if this feat were in effect for all collateral saves. However, if the spell includes two saves as part of its initial effect (e.g. Phantasmal Killer), the feat affects both as this is part of the spell "landing" on its target.