About 283 000 HP
Resistant to Libra,
Vulnerable to Dark
You will find Ultima at the top floor of Great Crystal. The way how to get there is in "Great Crystal II" part.
Ultima uses three attacks: Redemption, Holyja and sometimes Greater Barrier. Redemption and Holyja have Holy element. It is easy to disable them by wearing Sage's Ring or White Mask. Due to that instead of causing damage her attacks will heal you. Holyja may also cause Reverse, but since this attack didn't hurt you, no one from your team will try to heal you, and her normal attacks will keep healing you, so there's nothing harmful in that. There's still the matter of Greater Barrier left - what can I say - use dispel on her, when she uses that attack.
During this fight Fomalhaut with Dark Shot works well, berserked Yagyu Darkblade (eventually Orochi) and Darkga.
As you can see her attacks are nothing special so there must be something inside it. The thing is, all the "obstacles" you had encountered during the game will appear one by one in this order:
- Drain HP - slowly drains HP,
- Drain MP - drains MP,
- No Attack - you cannot attack with weapons ,
- No Magick - blocks magick,
- No Technicks - blocks all your technicks,
- No Items - objects are not available for you,
- Magnetic Field - electrostatic field that makes moving difficult, especially for those in heavy armors.
If you conform to my advices, have to face all of those obstacles (the fight will be over sooner) and will get Ultima without bigger problems.