Instructions
Attack Seymour
Put whoever has a Stonetouch/strike weapon in the first group and have them attack Seymour's cronies. If you do not Stone them or kill them in a single hit, they will forever Auto-Potion whichever one of them is hurt.
Smack Seymour until he summons his Aeon, Anima. This monster is extremely dangerous and does a massive Pain attack, in addition to an Overdrive attack that spells certain death.
Use your Aeons to hit Anima, then Shield them when Anima's Overdrive gauge gets near full.
Use your Aeon's Overdrive to finish Anima and Seymour. Although Shiva's Overdrive works the best, Ixion can start with a full Overdrive gauge if you came in prepared.
Pound Seymour into the ground, then suffer the ire of his servants as they call you traitors and destroy the evidence of his treachery.
Escape From Macalania Temple
Run from Macalania Temple at full speed. The Guado are chasing you and will keep chasing you until you escape. Stand and fight for a while if you want to rack up some levels, but there are better places to grind.
Continue using your Stone/Death touch weapons because the Guado you'll be fighting will still have the Auto-Potion ability.
Take the path on the right-hand side as you leave the temple. There's a chest at the end with a Level 1 Key Sphere.
Re-equip and get geared up at the save Sphere. There's another boss coming up.