When you arrive here, by the Highroad or low road, talk to the person by the Chocobo. You need to rent one for 1000 gil. If you can't afford it, start selling junk or fighting. If you killed the Chocobo Eater, you get a Chocobo for free. Now that you're on it, go through and continue (no random fights on Chocobos) and look for special areas. Press X near the ledge, and the Chocobo can jump to inaccessible areas. Look for areas with rocks to jump to. There should be an area on the left side you can get back in the low road area, by O'aka.
Try to go through the Mushroom Gates and you will learn you cannot pass. Talk to the man on the left and he explains the upcoming operation. You can donate money to the cause.
100 Gil - Scout (Wakka Weapon)
1000 Gil - Ice Lance (Kimahri Weapon)
10000 Gil - Moon Ring (Yuna Armor)
But most likely, you can only hand over 100 or 1000 by now. Walk away from the gates and it turns out Maester Seymour is there. For once, he's useful! Yuna explains the situation, and Seymour orders the Guards to grant them access. Follow Seymour and get ready.
Follow the mini-map through this mini-maze. You will get to dead ends frequently, but investigate strange looking rocks to find out they are platforms that lead to other areas. Go through this huge area, and you will find the Command Center at the end.
There is a field of forbidden Machina. Head through all that talking to everyone the whole way. O'aka is also here, overpricing his weapons. Head further on and keep going until you see the Save Sphere on the map.
Go to the Save Sphere and save the game. Head inside the tent and follow the Mini-map. Eventually, the map leads you to a guy. Talk to him and say your ready.
The cage full of Sinspawn is put out over the ocean, and once the cage is opened up, and the Sinspawn fall into the sea below. Unfortunately, it turns out that one of them can fly and it attacks you.
Sinspawn Gui
Head: 4000 HP, Body: 12000 HP, Arm: 800 HP each, AP: None
Steal: Grenade
Make sure Yuna and Ifrit are at overdrive. Go into battle and summon Ifrit and have him bring out his overdrive twice. This should take care of the head and both arms...for now. The arms regenerate. If it didn't take out the head have Wakka beat it a few more times and Lulu cast some ara spells on it. Next bring in your tough hitters like Kimahri, Auron and Tidus and have them beat the crap out of the body. After three turns the arms regenerate. Bring in Lulu to cast "ara" spells on them to get some overkill points, and you can now continue attacking the body. I seriously suggest having Tidus cast haste on most everybody especially Yuna because you'll need to her in to heal a lot.
After the battle, witness Sins attack. Hundreds are killed as Sin unleashes a barrier. But it turns out the Sinspawn Gui isn't dead! Seymour joins the fight.
Boss: Sinspawn Gui
Head: 1000 HP, Body: 6000 HP, Arm: 800 HP each, AP: 1514
Steal: Nothing
Experiment with Seymour�s magic attacks. Attack anything with Seymour and it will die in 1 turn, except the body.
When Tidus sees all the dead people, Sin starts to back off. Tidus jumps in the water and swims after Sin. Tidus ends up washed ashore. Talk to the party, then have Yuna perform the sending.
