Location Found: Baaj Temple
Anima is Seymour's Aeon. Her first appearance is after the Blitzball game in Luca. Seymour also summons her in battle against you while at Macalania. However, you can also get this powerful Aeon to fight for you.
You can obtain Anima by destroying the Destruction Sigil in each Cloister of Trials, then going to Baaj Temple, which can be found with the right coordinates. Once there, dive into the water from the rocks north of you, then swim towards the entrance of the temple to find...
HP: About 32.000
Sensor: Vurnerable to magic.
Immune to: All negative effects, except for Poison. However, there is another way to inflict negative status on him...
Stone Punch - Physical damage and Petrification to one character.
KO Punch - Physical damage and Death to one character.
Eat - Will eat one character. Will copy ALL status effects, including positive ones. Will later spit character out, inflicting damage to all characters equal to the amount of HP the character had when he/she was eaten. If you use Struggle inside his belly, he will spit you out immediately meaning instant KO, I do not know if this means damage to the party too. If you kill him with someone in his belly, he will spit the character out inflicting 9999 damage to the party.
This is the fiend that almost had Tidus for lunch in the beginning of the game, like Tidus said: "Payback time!" Death and Stoneproof armour is needed, trust me. At least use Stone Ward, because if you are petrified underwater, you will shatter and won't come back for the rest of the battle. First start out by inflicting Poison on Geosgano. I mixed up an Aqua Toxin with Rikku (Candle of Life, Fish Scale), because no one could use Bio. Then start inflicting status effects on one of your own characters. If one of your characters knows Cura(ga), inflict Zombie. I'd also recommend Slow. If Geosgano is zombified, cast Cura(ga)'s on him until he dies. Be sure not to kill him with a character in his belly! This will probably mean instant KO, which means you'll get Game Over. Good luck!
Her special attack is "Pain". This attack inflicts damage and Death to the opponent. The first time you see Anima is after the Blitzball game that you get to play at Luca when all the fiends start attacking. That is also the first time you see "Pain".
Her Overdrive is "Oblivion". If used, Anima takes enemies into oblivion (hence the name). Inside Oblivion, she breaks the chains that ties her hands down and delivers hit after hit. This means that you don't need Break Damage Limit to inflict a lot of damage with this Overdrive.
When you first get Anima, she comes with all elemental Black Magic spells, plus Bio and Death. She also comes with a lot of status inflicting attacks, including Zombie Attack.
If you have ever seen the first Lord of the Rings Anima's lower half looks like the the ring hunters (the guys with the black hoods) when Frodo puts on the ring. It doesnt look exactly like them but they look some what the same.