HP: 65,000

This battle is very similar to the fight against Evrae on the exterior of the Airship. The Fin will attack less frequently if you use the Trigger Commands to have Cid pull the Airship further away from Sin.

The Airship starts far away from Sin, so you will have to use the “Move In” command before you can initiate any attacks. Before you move the Airship closer, though, you should use the time in between to charge up your characters using Tidus’ Cheer ability, Rikku’s Luck ability, etc. Remember that you can use these abilities up to five times, and the effects will stack.

Use Hastega on your party early on, but be aware that the Sin can use an attack called “Negation,” which will remove any positive status effects from your party members. You will have to recast them afterwards.

Sin has a fairly high armor stat, so you may wish to use Auron’s Armor Break ability to help speed things up. But be aware that Negation will also remove the Armor Break negative status ailment from Sin. Just reapply it if Sin removes it.

If you see the message “Core Gathers Energy,” immediately use the Trigger Commands to pull the Airship away from Sin. Sin will be using Gravija shortly, which will hit for approximately 3/4 of each character’s total HP.

Steal:

• Mega-Potion (common)
• Supreme Gem (rare)

Drops:

• HP Sphere (common)
• HP Sphere (x2) (rare)

In Game Description: Unleashes Gravija once the core is energized, reducing all characters’ HP by 3/4. To avoid this, get Cid to back off. Dispels with Negation and sometimes attacks all with a physical attack.

This fight has the same battle mechanics as the previous fight.

Steal:
X-Potion (common)
Shining Gem (rare)

Drops:
Lv. 3 Key Sphere (common)
Lv. 3 Key Sphere (x2) (rare)

In Game Description: After losing half its HP, it enters its shell on its next turn. If hit there, it recovers with Cura and exits the shell on its next turn. Protected from Gravija when inside the shell.

HP: 20,000

Start this fight off by destroying Sinspawn Genais, which is the creature sitting in front of Sin’s core. Genais will absorb any magic that you try to use directly on Sin. This Sinspawn starts outside of its shell, unlike Sinspawn Geneaux which you fought at Kilika Temple.

Sinspawn Genais is weak to Fire-based magic attacks. It will also retreat into its shell once it goes below 50% of its HP and will begin casting Cura on itself. It does not have much HP (about 20,000), so hammer away at it with regular attacks until you bring it down.

You can cast Slow or use Silence Buster on Genais to prevent it from casting Cura (as often).

Steal:
Star Curtain (common)
Shining Gem (rare)

Drops:
Return Sphere (common)
Return Sphere (x2) (rare)

Sin (Core)

This fight is exactly the same as the Left Fin and Right Fin fights. The only difference is that you will no longer be able to dodge “Gravija” attacks by moving the ship around, and it will counterattack your regular attacks with low-level magic spells.

Sin may hit your party members with the Poison status effect. Have Rikku use an Al Bhed Potion, have Yuna use Esuna, or have any of your team members use an Antidote or a Remedy to remove it.

Steal:
Stamina Spring (x3) (common)
Stamina Spring (x4) (rare)

Drops:
MP Sphere (common)
MP Sphere (x2) (rare)

In Game Description: Pulls the Airship in while gathering all his strength to cast the ultimate terror, Giga-Graviton. Stop him before he wipes everyone out!

HP: 140,000

This battle has a time limit. After approximately sixteen turns, the fight will end as Sin will use its Overdrive ability, “Giga-Graviton,” which is an instant game over.

The charging bar above its head indicates how close it is to activating its Overdrive. Summoning an Aeon will not prevent death, which means you have to do 140,000 worth of damage before then.

Sin will start the battle being too far away for you to hit it, but it will slowly move closer (to within melee range) as the battle progresses. Use the first few turns to enhance your characters using Cheer, Luck, etc., and have Tidus cast Hastega on the party. Use either Lulu or Wakka in your party to do some damage even when Sin is at a distance.

You should have Auron use Armor Break once Sin gets close enough. Alternatively, you can have Rikku use her Mix ability and have her Mix two items (such as two Power Spheres or two Ability Spheres, creating a Frag Grenade), which can cause the same Armor Break status ailment.

Sin will begin attacking your party once it gets close enough to the ship, so be prepared to deal with the Petrify, Confuse, and Zombie status effects as they come. Good luck!

Steal:
Ether (common)
Supreme Gem (rare)

Drops:
Lv. 3 Key Sphere

In Game Description: Casts spells once energized by the four Mortiphasms behind him. Their positions somehow affect his actions. Physical attacks turn the Mortiphasms to the left, while magic turns them to the right.

HP: 80,000

The four floating discs behind Seymour Omnis are Mortiphasms. These discs will rotate throughout the battle, and the colors that are closest to Seymour will determine the strength and the element of the spells he will cast.

The discs have four colors: orange/red for Fire, yellow/green for Lightning, blue for Water, and purple for Ice.

Seymour will cast four spells every turn. If all four discs have a matching color, he will cast the strongest versions of the spells (Firaga, Thundaga, Waterga, or Blizzaga), and he will also absorb that element if you cast a spell of that type on him.

He will also be weak to the opposite element. If three discs match in color, he will absorb that element as well; however, he will no longer be weak to the opposite element. Two matching discs make him immune to the element, while a single disc will make him resistant to that element. You can use the Scan ability to verify his elemental strengths and weaknesses.

Seymour will begin glowing red after you attack him six times. He will also begin casting Dispel at this stage of the battle and will begin using Ultima against your party. He stops glowing red after he has cast Ultima.

Seymour’s Ultima isn’t nearly as powerful as the one accessible in the Sphere Grid, but it can still do some significant damage (around 4,000 HP to each party member). Make sure you heal up before he casts it and use the Shield command if you are having trouble surviving it. You can also use Lulu’s Focus spell or Yuna’s Shell spell to increase your resistance to it.

This fight is one of the few against Seymour where you can utilize your Aeons. He will not banish them if you utilize them during the fight. You can also use Yuna’s Nul spells to reduce the amount of damage done.

Use Hastega on your party early on and use Armor Break and Mental Break. Just be aware that you may have to recast some of these spells if Seymour uses Dispel.

You can also attack the Mortiphasms to rotate them, reducing the likelihood of Seymour using his strongest attacks. Some of the Mortiphasms are in the back row, so you will have to use either Wakka or Lulu to hit them.

Steal:
Shining Gem (common)
Supreme Gem (rare)

Drops:
Lv. 3 Key Sphere (common)