Spiral Cut is an enemy ability used by Tidus in the Fiend Arena, which just deals moderate non-elemental physical damage to one party member. This ability is not used when Tidus is controlled by the AI in the party.
Spiral Cut is a water-elemental physical attack command ability. The ability can only be learned from the Tidus phantom stone. There are three types of Spiral Cut abilities available, with their overall potency and MP cost rising whenever the player's summon ranks up. The ability deals heavy water-elemental physical attack to a single enemy.
Spiral Cut is one of Tidus's equipment Soul Breaks available from the sword Brotherhood (X) which at the expense of one Soul Gauge segment unleashes a powerful attack on all targets which deals physical damage equal to 480% power of a conventional attack. Bringing Tidus to battle and emerging victorious with Brotherhood (X) equipped, he can eventually master this Soul Break and be able to use it without the need to have it equipped.