The Mysterious Girl will be joined by Ifrit during this fight. The battle cannot be won.
Porom will be assisted by the Elder of Mysidia during the fight. He has access to all White Magic but Holy. Like Palom's fight, this is mostly scripted. Use their best attacks until the Mysterious Girl uses Ramuh to defeat both of them.
Golbez and Fusoya will fight the Mysterious Girl, who has summoned Asura at the start of the battle. Asura cannot be defeated and their attacks must be focused the Mysterious Girl. She will attack them with strong magic such as Flare, Holy, and even Meteor. Fusoya and Golbez must use spells like Firaga and Flare on her while withstanding her and Asura's attacks. Whenever either of them are weakened, Fusoya should use Curaga or Curaja. If Golbez is ever KOed, it would be best to revive him with Arise.
The fight is nearly the same as the last, but the Mysterious Girl has now instead summoned Leviathan. Leviathan will use Tidal Wave even as the Mysterious Girl uses the strong spells she had from the previous fight. The same strategy for the first battle fought in the crater still works, but Fusoya should focus more on healing both him and Golbez. Leviathan's Tidal Wave is strong, and it can KO one of them if they have already took a lot of damage from the Mysterious Girl.
After fighting Odin, the party will then face the Mysterious Girl. Golbez, Ceodore, Rosa, Rydia, and Edge will fight her. The Mysterious Girl still will not hesitate to use strong magic like Flare on anyone. Ceodore should use Awaken at the start of the fight and use it to its full potential before the effects run out. Rydia and Edge's best strategy is to use the Band ability Inferno, which will do around 1,500 - 2,000 damage to the Mysterious Girl. Golbez's best magic to use against her is Flare. Because Rosa is the only healer that joins the fight, she should use healing spells every turn. If she has learnt Curaja from Kain's Tale, she should cast it on everybody. Another alternative method is to search for a band as Rydia or Rosa and select the others magic command, this will cause holy burst which also does tons of damage, and if you do this, you should make Edge the main healer with his heal pill and have Ceodore use Cura or Curaga when needed. When the Mysterious Girl nears death, she will attempt to raise her power so she can cast Meteor. This is the party's chance to kill her quickly before she attacks, which should not take a lot of damage to do. If the party isn't quick enough in killing her, she may potentially summon Asura, Leviathan or Bahamut to aid her or hurt the party, which Rydia will unhappily comment on.
Final Tale: Planet Eater
Template:FFIV:TAY Enemies Bahamut will be summoned at the start of the fight. The Mysterious Girl will use Black Hole before Megaflare with no turns in-between, making Reflect useless against Megaflare. Reflect should still give some protection against the Mysterious Girl's magic. If Rydia defeated Asura and Leviathan on the True Moon Subterrane and learnt how to cast them, then they will appear during the fight to reason with Bahamut. He will eventually come back to his senses and fight back against the Mysterious Girl.