As you start the game talk with the people around you, and as soon as your through signing autographs just walk around till the preparation for the Blitzball match occurs. Walk your way through the people and to the stadium, and after a long and dynamic FMV you’ll find yourself in the heat of battle. Apparently this “Sin” is the source of havoc, and you find Tidus and Auron defending themselves. Just hack and slash away at the Sinscales; they only have 100 HP and Tidus and Auron can both take them down with one hit. So save your Overdrives for the upcoming boss later, if by a chance you did earn them.
Several of these Sinscales will get in your way, and you’ll have no choice, but to fight them. Try to avoid attacking the ones that come from behind since your main goal is to run towards the larger target.
This battle cannot kill Tidus and Auron if you destroy the Sinscales first. The boss will always cast Demi, cutting down your HP in half each time. So anybody familiar with this spell would know that it cannot kill. Avoid healing since it will do you no good until after the battle and just attack as normal. Also, regardless of whether or not you earned an Overdrive in the previous battles or not, you will have your guages nearly full. You probably won’t be able to perform the Overdrive motions in the amount of time they give you, but that’s okay! You’ll learn to master them later as you see it more often, and as it builds your way into your long term memory.
There’s a save point just behind the defeated Sinspawn Ammes. Feel free to save your game. After the battle keep running, you’ll encounter a swarm of these Sinscales. You’ll have to wait a while and have Auron tell you about destroying the generator to the right. Unfortunately the last battle left you pretty weak, and you can’t attack the generator before Auron signifies to do so.
Ddingojellybean – Author of the walkthrough