In the second battle, Seifer is faced alone. In the third battle, Edea joins Seifer. At the fourth battle, Seifer is again faced alone. The player can prepare for each battle by junctioningFire to elemental defense, as Seifer always uses Fire magic.
Seifer is fought one-on-one with Squall at Edea's parade. Seifer's strongest attack is the Fira spell, which he will rarely use. Instead, he will usually attack with the Hyperion, which will occasionally trigger, dealing slightly more damage.
Seifer is fought in Galbadia Garden. Drawing and casting Haste will make the battle go faster. He will not use Fira, instead preferring to attack with gunblade attacks and the Hyperion still only triggers rarely. When his health is sufficiently low, he will say "Ready to die Squall?", and will attack Squall with Demon Slice, which deals roughly 1500 damage. After that he will start to use Demon Slice regularly, as well as continuing to use his physical attack.
Seifer is now joined by Edea, but she will not attack, choosing merely to watch the fight. Seifer, still recovering from the last battle, has less HP. His attacks are more powerful, and he once again uses Fira. The easiest way to defeat Seifer is to draw and cast Haste on the party, and simply attack him. Keeping an eye on his HP may be wise, as renewing Haste on the party will help with the next battle. When Seifer falls Edea will intervene, triggering another boss battle.
Seifer is faced for the final time in Lunatic Pandora. He has changed in both attitude and appearance. His coat is ragged and he now sees himself as a revolutionary. Seifer attacks with physical attacks, and at low HP employs a new attack, Bloodfest, which deals high damage to the entire party.
The player should equip Mug to steal a Hero from him and draw Aura spells, as Seifer is the only opponent in the entire game who possesses it. If the party has obtained the GFOdin, he will be summoned, but Seifer unleashes Zantetsuken Reverse to slice Odin in half.
Gilgamesh claims Odin's sword. If the battle is not won within 13 turns, Gilgamesh arrives and defeats Seifer. If the player deals enough damage before the turn limit, Gilgamesh will also appear. If Odin has not been obtained before this battle, Gilgamesh does not appear, and is unobtainable for the remainder of the game.
The gunblade models in these battles exist separately from Seifer. This is how all player characters work, and Seifer is a temporary playable character with this weapon. Due to this, the gunblade models count as enemies though they are never targetable. They are called "Gunblade" and have Gerogero's Scan information.