Dark Ixion
Dark Ixion is one of the Dark Aeons and spawns after you have obtained the airship Fahrenheit. Dark Ixion can be found in the Thunder Plains and defeating it involves challenging it to two separate fights.
Location
Head back to the Thunder Plains and head in to the northern section and look for a Yevon soldier. After you defeat Dark Ixion for the first time, you will have to seek it out one more time. Ixion will spawn very close to the party after the next lightning strike.
Battle Preparation
Each of the Dark Aeons, including Dark Ixion, are considered superbosses and are some of the strongest enemies that you can fight in the game. As such, you will need to ensure that your party is fully leveled, has their best weapons and has their stats maximized as much as possible. Refer to the Advanced area of the Tips and Tricks section for additional details.
You do not need to have an specific armor equipped although it helps to have the 
Auto-Phoenix auto-ability on at least two of your party member’s armor.
Dark Valefor Stats
HP: 1,200,000 (x2)
Elemental Affinities: Absorbs lightning damage, Holy damage hits for double
Immune to Sensor
Battle Strategy
Dark Ixion will automatically counterattack all of your attacks with a regular attack of its own. This attack is fairly easy to dodge if your Evasion stat is maxed out on each of your characters, otherwise, prepare to heal your characters between each of Ixion’s attacks.
Make sure to keep your party members equipped with 
Auto-Life at all times just in case Dark Ixion gets that chance to use its Overdrive, Aerospark.
You can escape this battle at any time if you run in to trouble by using the 
Flee command.
Items and Rewards
You can Steal the following items during the battle:
Stamina Tablet (x2) (common)
Elixir (rare)
And Dark Valefor will drop the following items when it is defeated:
Dark Matter (common)
Master Sphere (rare)
