This rapier like weapon has a thicker blade than normal, which is shaped into a corkscrewing spiral of sharpened edges. These edges can catch enemy weapons, making it ideal for disarming or parrying.
You can use the Weapon Finesse feat to apply your Dexterity modifier instead of your Strength modifier to attack rolls with a spiral rapier sized for you, even though it isn’t a light weapon. You can’t wield a spiral rapier in two hands in order to apply 1-1/2 times your Strength modifier to its damage. Any effects that apply to rapiers also apply to a spiral rapier.
Pathfinder Player Companion: Adventurer’s Armory 2 © 2017, Paizo Inc.; Authors: Jenny Jarzabski, Mikko Kallio, Isabelle Lee, Luis Loza, Joe Pasini, David N. Ross, and Linda Zayas-Palmer.