Centra Ruins (Odin Side Quest) - FF8 Guide
The Centra Ruins is located on the southern most continent and can be easily reached once you gain control of the Balamb Garden during Disc 2. There's two GFs for you to obtain here, Tonberry King GF as well as the Odin GF. Odin doesn't work like a typical GF in the sense that he isn't Junctionable - nor does he appear on your GF list.
Instead, Odin has a random chance of showing up at the start of battle and he'll instantly defeat the enemy when he does. If you get Odin before the end of Disc 3 then he'll be replaced with Gilgamesh who is significantly worse than Odin. Gilgamesh has a chance of showing up randomly during any battle and he can do 1 of 4 different things, each with a 25% chance of happening. One of which is Excalipoor which does 1 damage to the target.
For anyone who plans to do the Angelo Search farming method it's highly recommended you do NOT get Gilgamesh as he'll compeltely ruin this farming method. That means you will have to wait until Disc 4 to acquire Odin - or do all of your Angelo Search farming prior to Disc 4.
When you're ready to begin the Odin quest you'll want to go up the elevator in the Centra Ruins to the upper portion of the dungeon. The elevator is found a few rooms deep in the dungeon, the path to it is completely linear.
After going up the elevator you will find two ladders carved into the stone wall, take the left one up to the top where you'll find an orb which after examined will begin to glow (pictured below). Travel back down to the area with the elevator and examine the now glowing orb here to reveal a staircase to the right (pictured below).
You'll want to go up the newely revealed staircase and follow it until you reach a new area with a ladder to the left and a staircase to the right. Take the ladder on the left to a gargoyle statue with only one eye (pictured below; left). Remove the eye from this gargoyle statue then go up the staircase nearby - keep going up until you find another gargoyle statue (pictured below; right).
When you place both eyes into the gargoyle statue at the very top of Centra Ruins you'll get a code. You need to remember/write down this code then take both eyes out of the gargoyle statue at the top of Centra Ruins and put them into the one below you.
As far as I am aware the code changes with each save file (much like the Deling City/Tomb of the Unknown King part of the game on Disc 1) so using my code below won't work for you.
Important Odin Junction Tip: Make sure you equip Draw to each character as well as Mug to one character. You can Mug a Luck-J Scroll from Odin!
Once you have input your own code the door below the gargoyle statue will open up and you'll be able to enter to fight Odin. He's sitting on a throne just inside the room, approach him to engage and begin the battle. If you don't have much time left on the timer in the top left of your screen you'll want to wait until you're ejected from the dungeon then come back and try again.
Odin Draw Information: If you don't have Triple or Double on your characters you can Draw it from Odin during the fight
Odin Mug Information: Make sure you Mug the Luck-J Scroll from Odin!!! This is an extremely rare and extremely useful item!
Odin doesn't attack for this entire fight - the only way he will attack you is if you don't defeat him before the timer expires at which point he'll use Zantetsuken on you and your group. Zantetsuken is a guaranteed Game Over, incase you didn't know.
All in all this fight shouldn't be very hard, at level 100 Odin only has 30,000 HP which means he'll likely go down in just a few hits depending on how good your Junctions are. Just make sure you Mug the Luck-J Scroll from him - if you don't then reset the game. That scroll is arguably more important than Odin himself.