Waking Nightmares

[The Total Package]

You fill the creature's mind with a terrifying vision. The target must attempt a Will save. A creature frightened by this spell takes 1 additional mental damage each time it's hit by a Strike.

Critical Success The target is unaffected.
Success The target is frightened 1.
Failure The target is frightened 2. If it's asleep, it wakes up and is paralyzed for 1 round.
Critical Failure As failure, but frightened 3.

For the Duration it states: varies

My question is does the mental damage only last for as long as the frightened condition is on the enemy, or does it stay on until the creature indefinitely as long as they don't critically succeed the save. It's not so clear.

[Baarogue]

Since the mental damage is a rider on the frightened condition I would rule the duration has to last until their frightened expires, but no longer

[shroudb]

"A creature Frightened by this spell" I take it as "if it's no longer frightened by the spell, the conditional stops applying".

It can be nasty though with options that stops the frightned to drop.