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If you're either not interested in, or have already done, most of the sidequests that Final Fantasy 10 has to offer, then this will be the final stop for you. If you've not done most of the smaller sidequests, before you make any progress through Sin you should go and do them; the fiends inside Sin are quite difficult in their own right and the bosses are even harder. However, it is a good idea that if you are intending to get a full experience out of this game and challenge the likes of the Monster Arena and the Dark Aeons, then take the liberty of completing this game before you get too powerful; otherwise the bosses become far too easy and it makes the ending seem a little anticlimactic.

Contents 1 To Sin's Nucleus 1.1 Boss Battle: Seymour Omnis 1.2 The City of the Dead 1.3 Inside the Nucleus 2 Meeting Jecht 2.1 Braska's Final Aeon, First Form 2.2 Braska's Final Aeon, Second Form 3 Confronting Yu Yevon 3.1 The Aeon Battles 3.2 Final Boss: Yu Yevon 4 The End of the Journey

[edit] To Sin's Nucleus

First of all, you've got a sort of endless sea to navigate. You'll be on a watery pathway surrounded by various glyphs and symbols as you make your way northwards towards the arrow. Make sure to explore this place fully; the experience from the monsters will help tremendously (they all have a high AP yield) and there are a lot of good items to get. There is a Phantom Ring and Special Sphere on the left-hand side, and a Wizard Lance and a Level 3 Key Sphere on the right. There are several new monsters here:

• Behemoth Kings have 67,500 HP and are basically a tougher, stronger, and more dangerous version of the Behemoths of Mt. Gagazet or Zanarkand. Power and Magic Break it (this halves the damage dealt by Heave and Flare), but be wary. If you kill it by normal means, it's last gasp move is Meteor which hits the entire party for 6000 damage; you won't be able to survive this. So, whack out your Capture weapons and make sure you land the final blow with one. Not only do you get the capture, but you avoid a painful, fiery death. Watch out as well; they will cast Mighty Guard once they get low on HP. Kimahri can learn it off them with Lancet, otherwise just Dispel it and carry on the assault.
• Geminis come in two types; both have 36,000 HP, and both are armoured, but one has a club and absorbs ice and water elements, whereas the other has a sword and absorbs fire and thunder. Armour Break and Triple Foul work very well indeed on them, and just pound away at them until they die. Remember they both count as unique fiends if you're trying to capture them, and you need one of each to complete the area (or 10 if you plan on unlocking Ironclad at the arena).
• Adamantoises have 54,400 HP and absorb fire. They're armoured, so use Armour Break, otherwise just wear them down; they're quite slow and vulnerable after getting rid of their armour. The only problem is their Breath and Earthquake attacks which does about 1500 fire damage/physical damage to everyone respectively; nullify this with NulBlaze or appropriate armour auto-abilities, or Protect/Shell. Adamantoises also have practically no resistance to anything caused by Triple Foul, so use that to render it completely harmless. However, it is immune to Demi, but not Bio so if you feel like letting it die in its sleep by poison, go ahead.
• Exorays have only 7,400 HP (killable in one hit from either Yuna's Holy, Auron, or possibly Wakka and Tidus if they're strong enough) but if you fail to kill them in that one hit, it will retaliate with Pollen which really screws up your party with a variety of nasty status effects such as sleep, poison, silence and darkness. The fact that they only really use Firaga outside of that which is a magic attack (and as a result, does not wake up sleeping characters) might lead to a rather sticky situation.

Note that if you've got Yuna's Nirvana by now (which is entirely possible even with only a little amount of time spent doing sidequests) and all her Aeons she will easily be the most powerful attacker, with her Holy costing 1MP and inflicting anything up to around about 20000 damage.

Also, you may be wondering where to take your characters after they've finished their Sphere Grid sections:

• Yuna should move onto Rikku's section and follow it back to the start, then into the area where Kimahri started and begin unlocking her way to Ultima (this allows you to ruthlessly exploit One MP Cost on her weapon and abuse her very high Magic stat much earlier than you could with Lulu).
• Lulu probably hasn't finished her Sphere Grid section yet, but if she has, move her along Wakka's section to learn Drain and Osmose. If Yuna learns Ultima, use a Black Magic Sphere to teach Lulu it, too.
• Rikku should move along Lulu's section of the grid (starting with the -ara elemental spells).
• Wakka should move onto Auron's section and work his way back to the start (Power Break); this will bolster his Strength tremendously.
• Tidus should move along Auron's section too; the copious amounts of Strength +4s will give Tidus a license to inflict 9999 damage (until he can break the damage limit).
• Auron should move along Tidus' to Quick Hit; this is necessary to bolster Auron's pretty pathetic Agility and Accuracy stats.
• Kimahri is Kimahri. He should be non-one-hittable. Otherwise, level him up…or don't use him.

Keep heading north and you'll find a save sphere at the base of some stone steps. Save, then equip all of your best elemental resistance armours and head up them. That's right folks, he's survived death three times and now he's back deadlier than ever. Say hello to…

[edit] Boss Battle: Seymour Omnis

Seymour's a little more powerful than before. Just a little bit. And he's gone a little crazy.

He's got 80,000 HP, firstly. This is a lot, but thankfully you've still got the one-turn grace of an Aeon with which to use an overdrive if you have one ready. Seymour's defences are pretty high so don't expect them to do that much damage, not to mention some are capped at 9,999 a hit, you've got to take into account Seymour's current elemental resists, and the Mortiphasms won't take more health off Seymour for you.

The Mortiphasms (the large circles around Seymour with the coloured circles on them) will help you determine his current elemental power:

• With all four of one colour (i.e. red) are pointing towards him, he absorbs that element (in this case, fire) and is weak (1.5x damage) to the opposite (in this case, ice).
• With three of one colour and one of another, he absorbs that element (red = fire, as before) but is not weak the opposing element and halves damage from the other element.
• With two of one colour, he nulls damage from it.
• With one of a colour, he halves that damage.

This is the same with all the other elements. However, he will also, with each attack, cast four Firagas at your party; this hindsight is necessary for giving Yuna long enough to add the appropriate Nul spell to counter his pretty vicious magical attacks. Seymour doesn't quit there, either; he's got Flare and Ultima to back them up (Ultima does about 5,000 to everyone — ouch) and, to top it off, Dispel (to eliminate your protection). The elemental resistance armours like the Phantom Bangle, Phantom Ring and Victorious are absolutely crucial in granting your party protection from his elemental attacks when the Nul spells can't save you (he tends to counter with his other spells a lot, but mainly Flare and Dispel). Thankfully, you'll get a warning when Ultima's on its way (he'll say a little speech, glow red, and Dispel your party); use an Aeon to throw Seymour's turn out of whack (he may even cast it on your Aeon, who can soak up Ultima far better than your party can).

The specifics of the Mortiphasms are as follows.

• Seymour's normal turn, providing he's not preparing for Ultima, will always consist of four spells.
• If there is four of one element, he'll cast four of that element's -aga spell.
• If there is three of one element, he'll cast three of that element's -aga spell and one of the other element's -ara spell.
• If there are two of one element, he'll cast two of that element's -ara spell.
• If there is one of an element, he'll cast one of that element's -ara spell.
• For example, if there were two fire, one lightning and one ice, he'll cast two Firas, a Thundara and a Blizzara. If there's three water and one fire, he'll cast three Watergas and one Fira.

As for damaging Seymour, Overdrives, Aeons (note: you can summon Anima for an interesting retort; remember who Anima actually is?), and not forgetting Holy, are all excellent ways. He's immune to pretty much every status effect like Slow, Delay, Silence, Darkness, Sleep and Power, Magic and Armour Break. Seymour has, unfortunately, finally fixed his random weakness to Poison but he isn't immune to Mental Break.

[edit] The City of the Dead

Once you've beaten him, Yuna will send him, and you'll get the after-battle screen, then progress into a new area of Sin. There are quite a few new enemies to contend with now, as well as returning ones from the Sea of Sorrow section:

• Wraiths have exactly 22,222 HP (?) and their first turn is always Doom. They have a variety of other spells like -aga spells and Death, so watch out. They're resilient to physical attack but don't forget the Holy treatment. They are weak to Holy, but do not take their magical resistances as shown by Sensor the first time to be certain; every Wraith has different resistances.
• Demonoliths are enemies in the same level of sheer annoyance as the Great Malboro. They have 45,000 HP, they halve all normal elements, and are armoured. They have a grand total of three attacks; one is a claw attack which hits for about 2000 damage to one person but can inflict Zombie, another is Pharoah's Curse which it will counter-attack pretty much EVERYTHING with, and it inflicts Poison, Curse, Darkness and Silence. But worst of all is Breath. Unlike the relatively tame one from the Adamantoise, this one petrifies your entire party. If no-one's immune or has any resistance to petrification there is about a 95% chance you will instantly get Game Over. Your best bet is Doublecasted Demi or Flare, one person takes a Pharoah's Curse to inflict Armour Break, or a Holy. If you're trying to capture one…good luck.
• Great Malboros are pretty much exactly akin to the Malboro of the Calm Lands but instead it's got nearly two and a half times as much health (64,000 HP, yes, only 16,000 less than Seymour) and always uses Bad Breath on an ambush, otherwise a 1/3 chance on every turn it gets. Thankfully the Great Malboro is still incredibly slow which although cannot be manipulated with either Delay or Slow you can use Hastega on fast characters and use the likes of Quick Hit; even with the amount of health it has, repeatedly pummeling it with physical attacks quickly builds up damage.
• Barbatoses are pretty rare, but they're also impressive; a staggering 95,000 HP (more than Seymour) and they're armoured. To start with, Armour Break it (this thing even has a resistance to Armour Break; it might not work first time), then follow up with repeated physical attacks, pummeling with Holy and Demi (a Doublecasted Demi at any point with it above 40,000 HP will hit for precisely 19,998 damage). It has three attacks, a one-arm smash which hits one person for about 2000 damage, Body Splash which is a physical attack hitting everyone for around 1500, and Mortar which is a magical attack hitting everyone for about 2000 damage and delays their turn.

In the first area of the City, stick around by the glyph on the right until you've killed a total of 30 fiends; then it'll open for you, revealing a chest containing a Level 4 Key Sphere. At the bottom of a long slide to another area of the city further along is a Laevatein in a chest, behind a glyph wall in a secret alley on the left hand side of the area is a Megalixir and at the bottom of a small lower section in one of the open areas is a chest with 20,000 Gil. Carry on along to either red arrow (there are two pathways you can take out of this area) until you get to the long path leading to a seemingly endless section of the city. As you approach, a giant tower covered in glyphs will drop from the sky.

WARNING: THIS IS THE POINT OF NO RETURN. THE MOMENT YOU TOUCH THE BIG CENTRAL GLYPH AND ENTER THE TOWER, YOU ARE INSIDE THE NUCLEUS AND CAN NO LONGER RETURN TO YOUR AIRSHIP OR ANY OTHER PART OF SPIRA. IF THERE IS ANYTHING YOU WANT TO DO IN THE GAME IN TERMS OF SIDEQUESTS, GO BACK TO THE SAVE SPHERE AND USE IT TO BOARD YOUR AIRSHIP AGAIN. REMEMBER, YOU CANNOT RETURN BEYOND THIS POINT.

Touch the big central glyph and you will be enter Sin's Nucleus.

[edit] Inside the Nucleus

If you remember the Battle of Mushroom Rock from earlier, you will have seen a load of Crusaders as well as Luzzu walking and running around hopelessly inside here. As you can imagine, the fact that there's so many unsent in such a small area creates a lot of rather powerful fiends. The "random" encounters increase in difficulty the further you get into Sin; in the Sea section it wasn't too bad, it became a lot harder in the city, but now you can even encounter the likes of three Demonoliths in one go and even some new enemies that you can't capture.

Your aim is to collect 10 of the glowing spheres which appear and disappear around the Nucleus from time to time, whilst dodging the spikes of ice which shoot out of the ground; touching one of these triggers an enemy encounter. As you collect more of the spheres (all of them give you pretty good stuff, it has to be said) the frequency and speed at which the spikes appear increases until it becomes pretty difficult to avoid them. Once you've collected 10 however, you'll be transported out of there and into another section of Sin.

[edit] Meeting Jecht

Go through the long scene and you'll start the battle with Jecht, who has taken on a more…dangerous form.

[edit] Braska's Final Aeon, First Form

Braska's Final Aeon has 60,000 HP in his first form, which is not too bad, but it wouldn't be the proper final battle if it was easy. Accompanying it are two Yu Pagodas; creepy-looking segmented rotating pillars. These are unique enemies indeed, as they cannot actually permanently die. They both start off initially with 5,000 HP but the attack which "kills" them (makes them stop functioning for a few turns, basically) will become the total HP it has next time around. For instance, hit one at the start for 7000 damage and next time it starts functioning, it'll have 7,000 HP.

However, this is not the problem. The Yu Pagodas have a move called Power Wave which heals Braska's Final Aeon for 1500 precisely, removes any negative status effects from him, and raises his Overdrive gauge by just under 1/5. Yes, Braska's Final Aeon has an Overdrive, and whereas it isn't particularly problematic in the first form it becomes DEADLY in the second. They often get turns together, so expect more often than not to see two Overdrive raises and 3000 HP healed. They will also retaliate with Curse (which inflicts Curse, Poison, Silence and Darkness) when either dies or with a variety of other moves depending on what you use against them.

Contrasting with most bosses, Braska's Final Aeon is weak to an assortment of different status effects, namely Poison, Zombie, Power and Armour Break, Confusion and Berserk. This means that Kimahri's Bad Breath Ronso Rage is useful, as well as Auron's Banishing Blade Overdrive and Zombie Attack. However, remember that you'll only be able to take advantage of this until the next Yu Pagoda turn comes up, because they will use Power Wave and remove all of them.

As for attacks, Braska's Final Aeon uses Jecht Beam which does up to about 1000 damage to one person and inflicts Petrification, a normal physical attack which can hit for 2000 and will reliably shatter a petrified party member (keep everybody healed up with Esunas, Softs or Remedies). His Overdrive is Triumphant Grasp, which does up to 4000 damage to one character. With regards to Aeons, Jecht will use Jecht Bomber, which also does up to 4000 damage, so watch out.

For this battle you can use a variety of strategies, but you'll want to try and keep everyone in Haste in order to give yourself enough turns. Try not to use too many attacks which push characters down the turn list, although Overdrives are acceptable. Blitz Ace/Attack Reels/Banishing Blade all work well, and Grand Summoned Anima, Bahamut or Magus Sisters will help in a pinch too. Providing you know what you're doing, Mix can help to give your party some vital assistance (especially with the Mighty G series of mixable items), as well as the aforementioned Bad Breath from Kimahri. Lulu might not be that useful for this fight, unless she's got a decent Magic stat beyond what she'd normally have by the end of her Grid section and has learnt Ultima and Doublecast, and preferably have a Half MP/One MP Cost ability on her weapon.

If the Pagodas are giving you trouble kill them both off to give you time to damage Braska's Final Aeon, or better yet cast Slowga. The main boss is immune to it, but the Pagodas are not and this will make them a lot less dangerous as they won't get nearly as many turns, they can be further Delayed, and the other Pagoda won't counter-attack, since you won't kill them off.

Lastly, Tidus has a trigger command, "Talk" for this battle (both forms). Do NOT use it in the first form. Triumphant Grasp is survivable. The Ultimate Jecht Shot is not.

[edit] Braska's Final Aeon, Second Form

Now it pulls a giant sword out of its chest and doubles its maximum HP to a whopping 120,000. That's only 20,000 less than Sin Overdrive, and this guy's a lot more resilient to damage. The first form is really a warm up for this one.

He has Jecht Beam still, and Jecht Bomber is reserved for Aeons again, but now Triumphant Grasp becomes a normal attack, his ordinary physical attack now does more damage, hits everyone, and has a delaying effect, and his Overdrive is replaced by the Ultimate Jecht Shot which is enormous and probably unsurvivably large amounts of damage to everyone. This is where "Talk" becomes useful.

"Talk" can be used a total of three times and will reduce Jecht's Overdrive gauge back to empty. This is good, because then you won't die when it uses its Overdrive on the next go. However, you must still be quick in damaging Braska's Final Aeon, as the Yu Pagodas will give you no respite from Power Wave and once you've run out of Talks you'd better get your highest-HP character out, Protect and Shell them, and hope for the best by defending. This may very well be Auron or Tidus, but there's no guarantee they'll survive.

Saving Overdrives for this battle might be a good move as Jecht does not get any faster and Slow will carry over on the Pagodas (providing you don't kill them). And, of course, taking the repeated battering from Braska's Final Aeon's attacks is now harder so you'll want to finish it off quicker.

[edit] Confronting Yu Yevon

Defeating Jecht will trigger another scene, and you'll be off into the true heart of Sin to fight the perpetuator of this whole nightmare, Yu Yevon.

[edit] The Aeon Battles

No need to worry about death, any more; all of your characters are in permanent Auto-Life status from this point onwards so none of them can actually ever die. They'll just get back up whenever they lose all their HP.

As requested by the fayth back in Bevelle, Yuna will summon all of her Aeons in turn (including the secret ones), who in turn will be possessed by Yu Yevon. Aeons are immune to all status effects including Sensor and Scan (the only one they aren't immune to is Curse, but you never get any attack which can inflict this). However, they have exactly the same stats and movesets as the original Aeons, so you can predict how tough they're going to be. You can choose what order you fight them in, but it doesn't matter since you have to fight all of the ones you have regardless. The Yu Pagodas are also present in this battle but since your party members won't inflict much less damage than normal against the Aeons, each of them probably won't survive long enough to get a go, but just in case they do it'll be another pair of Power Waves which have exactly the same properties as before. Finish off the last one (make sure you do Sensor them, as they have a somewhat saddening parting phrase in the sensor bar) and Yu Yevon will show his true form.

[edit] Final Boss: Yu Yevon

Yeah. He's not that powerful at all, is he? The Yevon symbol on an overgrown spider. Really lethal. He has 99,999 HP exactly, and he's got three attacks; the first one is Gravija which hits for a slightly larger proportion of your current HP than Demi does and which he will use on every turn he gets, secondly he has Ultima (which he will rarely use) which will most likely cause 9999 damage to al your party members (bearing in mind they're constantly in auto-life) and finally he can use a Curaga counter which heals him for 9999. There are two pitifully easy ways to kill this guy (bearing in mind that Yojimbo died so you can't Zanmato him).

• Inflict Zombie on Yu Yevon with Zombie Strike, then follow it up with Life.
• Cast Reflect on Yu Yevon and let his Curaga counter heal you instead.

That's right, he's weak to Zombie and instant death by Life. Failing that, he won't use the Curaga counter every time and the damage you can inflict on him will probably be greater than he can restore. If you have a Break Damage Limit weapon, especially with Wakka, and a full Overdrive you can smash Yu Yevon into oblivion with it. And don't forget; everybody's got permanent Auto-Life, so if by some miracle you wind up selecting one of your own characters as an attack target by accident and killing them, they'll just come back. In fact, a Yu Pagoda Curse counter is by far the most dangerous move in this battle, and the chances are it won't last long enough to happen.

[edit] The End of the Journey

Defeat Yu Yevon and you have killed Sin once and for all, forever. Isn't that great? You'll be treated to a nice long series of closing movies, and can re-load your last save to carry on with the sidequests, as if your daring defeat of Sin never happened. There are many extra parts to this game, and the Monster Arena/Dark Aeons/Penance are all there for you to test your mettle against the toughest enemies Square has come up with for a long time.