Seymour (Final Fantasy X boss)

The first battle with Seymour Guado occurs shortly after Yuna receives her fourth Aeon at Macalania Temple. Tidus and the other Guardians had discovered Seymour's treachery in murdering his father and attempted to stop him.

At the start of the battle, Yuna, Tidus and Wakka can talk to Seymour using the Trigger Commands. Doing this will raise Tidus' Strength and Yuna and Wakka's Magic Defense. Seymour is flanked by two of his Guado Guardians, their first action is to cast Protect on themselves, while Seymour casts Shell on himself, which is a rather dastardly trick. The Guards will cover Seymour from physical attacks, and you won't inflict much damage on them with physical attacks since they have Protect. They can't cover magic, but then Seymour has Shell on him. Using Ixion's Aerospark might counteract this. The Guards will use Hi-Potions whenever they are hit with a physical attack, using Rikku to Steal these will prevent this action. They will also throw Confuse-inducing Shremedies at the party.

Seymour will cast spells at the active party in the following order: Blizzard, Thunder, Water, and Fire. Using Yuna's Nul spells will help negate any damage.

After his HP drops to 3,000, Seymour will summon his Dark Aeon, Anima.

Anima
When Anima appears, take Tidus' advice and summon Shiva. Defend against Anima's Pain and heal using the Ice spells until Shiva has a full Overdrive gauge. Diamond Dust will potentially do near max damage to Anima. From then, keep Shiva alive until Anima unleashes Oblivion and then just attack until she is dismissed by Seymour. If Yuna can use Grand Summon and call Shiva with a full overdrive gauge at the start, this part of the battle will go much quicker.

After Anima is defeated, Seymour will have returned to full health and his Magic power will be raised. Using Auron's Magic Break will reduce the effect of the spells slightly. Seymour will now vary his spells and will also cast twice in one turn, however by using the Nul spells and attacking with the two best fighters, the battle is sure to end in the party's favor.

Strangely, Seymour's Requiem Overdrive, which he had as a playable character in the battle against Sinspawn Gui, is not used by Seymour, nor is it implied that he ever had access to it.