The Skull Ripper has this effect: "Dread Visage"
"Dread Visage (Su): All creatures within 30 feet that can see a skull ripper must make a DC 18 Will save at the start of their turn in order to avoid becoming frightened for 1 round. If the victim recognizes any of the heads affixed to the skull ripper’s body as having once belonged to friends or allies, that victim takes a –4 penalty on the save.
A creature that succeeds at the save is immune to the dread visage of that particular skull ripper for 24 hours. This is a mind-affecting fear effect. The save DC is Charisma-based."
Does this effect apply at the start of all rounds if PC does not success the check?
Thank you.
The ability only has a radius of 30ft and when a creature gains the frightened condition it will attempt to flee on it's turn. Additionally, the frightened condition it imposes only lasts a single round. So, the only reason they would have to keep making saves each round is if it can't flee or the skull ripper is deliberately chasing them. But, under those conditions yes. They would have to make a save every round. The only way to become immune to it is by making a successful save against it.
A frightened creature flees from the source of its fear as best it can. If unable to flee, it may fight. A frightened creature takes a –2 penalty on all attack rolls, saving throws, skill checks, and ability checks. A frightened creature can use special abilities, including spells, to flee; indeed, the creature must use such means if they are the only way to escape.
Frightened is like shaken, except that the creature must flee if possible. Panicked is a more extreme state of fear.