The Final Battle

Griever adds a uniquely dangerous resource attack: it can erase entire stocks of a randomly selected spell, and if that spell is junctioned the affected character's stats can fall immediately. That makes a long defensive battle risky even when HP is under control. Cast Meltdown, use Aura and high-damage Limit Breaks, and Dispel Triple or other buffs when they allow Griever to accelerate its spellcasting. Doom should be removed or allowed for only if you are certain the phase will end first. Keep Shell and strong recovery available for Shockwave Pulsar, which can be used as Griever's final attack, and finish the phase before repeated magic-stock destruction weakens the party's junctions.

Helixes are summoned during Ultimecia's Griever form and exist primarily to strengthen the main boss. With at least one Helix active, Ultimecia gains access to Ultima; with both active she can add Meteor and regularly use Great Attractor, so destroying them suppresses the phase's most dangerous options. Helix itself can attack with Twin Laser, but its own offense is secondary, and Esuna and Dispel can be Drawn from it if needed. Ultimecia can summon replacement Helixes while the first stage continues, so either remove them as they appear for a safer fight or ignore them and push Ultimecia hard with Meltdown and high-damage Limit Breaks. The Helixes disappear automatically once the phase advances.

Ultimecia begins by selecting three of the six party members at random, so the first problem is getting the characters you actually prepared onto the field. If an unwanted character is knocked out and left down, Ultimecia eventually absorbs that character and replaces them with someone from reserve; if a desired character falls, revive them quickly before the same removal occurs. Once the intended party is active, cast Meltdown and use Aura-assisted Limit Breaks while keeping recovery ready for Maelstrom and her high-level magic. Do not leave anyone dead simply because another character can revive later?the absorption mechanic permanently removes them for the remainder of the battle. Conserve enough healing and Aura resources for the three

After Ultimecia junctions herself to Griever, the Helixes determine how dangerous the phase becomes. As additional Helixes appear, Ultimecia gains access to stronger attacks, culminating in Great Attractor and other heavy party damage once both are active. You can destroy the Helixes to suppress those abilities, but a well-built party is often better served by casting Meltdown on Ultimecia and pushing the main body hard with Aura-assisted Limit Breaks before the setup fully develops. Protect is useful against Great Attractor, and Shell helps with her strongest magic. Keep revival immediate and reapply essential buffs after transitions; once the phase is driven far enough, the Helixes disappear and the fight moves to Ultimecia's final form.

Hell's Judgment is the defining attack of Ultimecia's final form: it reduces every living character to 1 HP but cannot kill them outright. Keep a fast character ready with a Megalixir or strong group recovery so Ultimecia cannot follow it with ordinary magic and finish the party; experienced setups can exploit the 1 HP state for Limit Breaks, but only if the next action is under control. Continue using Meltdown and Aura for concentrated damage, and revive fallen characters quickly before they can be removed from the battle. Guardian Forces are poor shields here because Ultimecia can destroy them during the summon sequence. Later, her lower body appears and Draws Apocalypse before casting it; Apocalypse can be Drawn and used against her, or