One-Eye is a special enemy in Final Fantasy X created in the Species Conquest at Monster Arena. It requires at least four of each Eye-type fiends to have been captured, except for the Bat Eye, which is only encountered in Via Purifico, when capturing enemies is not possible. One-Eye uses the same model as the Evil Eye and Bat Eye.
One-Eye is immune to four of five elements (Fire/Thunder/Water/Ice), and has Auto-Regen. It can be difficult to hit with a normal attack, but its low Evasion stat will work in the party's favor. One-Eye has a couple of attacks that can prove dangerous to an unprepared party. Shockwave will hit all characters for magic damage and inflict various status ailments: Confuse, Slow, Sleep (by 10 turns), Darkness (by 10 turns) and Silence (by 10 turns). Black Stare targets the character with the lowest HP for physical damage and causes Curse. One-Eye will open with Shockwave, and prioritize using Black Stare afterwards; if used five times in a row, it will use Shockwave on the next turn.
One-Eye can drop weapons with the Triple AP ability (useful for getting weapons for the Don Tonberry AP farming trick) and armor with any combination of MP +10%, MP +20%, or MP +30%, the latter being fixed.
The simplest strategy at lower endgame levels is to use Sandy's Razzia twice (select "Fight!" and then "One more time!") or Anima's Oblivion once (in the HD, PAL, or International versions). Aeons are immune to the status inflictions and should survive the initial Shockwave, so the Magus Sisters should not have much trouble staying alive.
Another strategy is to use Auron's Banishing Blade Overdrive as first move. If Auron doesn't have his Celestial Weapon, or a weapon with the First Strike ability, having Tidus use Armor Break will also work. Wakka should use his Attack Reels Overdrive, landing all 2x to finish him off.
Alternatively, a well-geared Auron can kill One-Eye before it has the opportunity to attack: Auron with an Auto-Haste armor and Masamune. The player should guard with each party member until One-Eye attacks and kills the party. Now that Auron has 1 HP he will deal maximum damage with his Masamune, and should be able to kill One-Eye. A Strength stat of about 100 is sufficient.
- Fly Eye
- Grim Gaze