Aeons - Final Fantasy X / FFX / FF10

Aeons
Final Fantasy X introduces a new way to summon, summons have been replaced, or should I say renamed Aeons. Aeons add much more control and in my opinion improve vastly on the summoning system in the previous Final Fantasy titles.

Final Fantasy X allows much greater controller over the Aeons, or summons and instead of appearing and doing a random attack you instead have complete control over them like you would a normal character. Not only that they have a choice of two attacks and as many spells as they have learnt!

That's right, Aeon's even have abilities to customize!

Valefor

Valefor is Yuna's first aeon. He is fast and very evasive, he can dodge most attacks from the ground. He attacks fast with a peak from his beak to causes a good amount of damage.

Location: Besaid Temple
Special Ability: Sonic Wings
Overdrive(s): Energy Ray, Energy Blast
How to Break Damage Limit: Yuna's Nirvana

Ifrit

Ifrit is is the aeon gained from visiting the Kilika Temple. He has great strength but what he gains in strength he loses in defence and magic defence. He can absorb all fire type attacks so curing himself is possible by using a fire attack on himself.

Location: Kilika Temple
Special Ability: Meteor Strike
Overdrive(s): Hellfire
How to Break Damage Limit: Wakka's World Champion.

Ixion

Ixion is gained from the Djose temple. Ixion stays solid during battle, he has high defence and magic defence and good speed. He uses the huge horn to causes damage to a enemy and to use his Thor's Hammer. He absorbs lightning so he may heal himself.

Location: Djose Temple
Special Ability: Aerospark
Overdrive(s): Thor's Hammer
How to Break Damage Limit: Kimahri's Spirit Lance

Shiva

Shiva is the goddess of ice. She is obtained from Macalania temple and is a grand sight to behold. She uses ice type attacks and absorbs all ice type attacks so she may heal herself by using ice on herself. She has low strength but high magic power and magic defence.

Location: Macalania Temple
Special Ability: Heavenly Strike
Overdrive(s): Diamond Dust
How to Break Damage Limit: Lulu's Onion Knight.

Bahamut

Bahamut is the lord of dragons and is the first aeon obtained to break the 9999 barrier. Bahamut has very high strength, magic and defence but he lacks speed.

Location: Bevelle Temple
Special Ability: Impulse
Overdrive(s): Mega Flare
How to Break Damage Limit: Not required.

Yojimbo

Yojimbo is a paid agent who fights for money, he is obtained from the Cavern of the Stolen Fayth. He has four different attacks - Daigoro, Kozuka, Wakizashi and Zanmato. The more you pay him the better the chance of him using Zanmato (his ultimate attack, can kill absolutley any enemy including bosses in one hit).

Location: Cavern of The Stolen Fayth
First off make sure you have at least 240,000 Gil. Where you found Defender X there is a bridge, there is also a gorge underneath the bridge. Head down and you will find the Cavern of the Stolen Fayth.
Special Ability: None
Overdrive(s): None
How to Break Damage Limit: Auron's Masamune.

Anima

Anima is a the aeon of Maseter Seymour. It is acquired by returning to the Baaj temple, defeating Geogaeno and solving a small puzzle. Anima is the most powerful aeon in the game, she has the strongest overdrive in the game that can cause a max of over one million damage.

Location: Baaj Temple
After obtaining the Airship it allows you to return to the Baaj Temple. First off re-visit all the Cloister's of Trails making sure you have obtained the item which requires the Destruction Sphere in each one, then use the Airship to travel to the Baaj Temple and defeat Geogaeno. Inside the temple approach every statue in the temple then head forth to recieve Anima.
Special Ability: Pain
Overdrive(s): Oblivion
How to Break Damage Limit: Not needed.

The Magus Sisters (Cindy, Mindy and Sandy)

The Magus Sisters are some of the most powerful aeons. Together they act as 3 different people and each one can do a special attack and all sorts of magic. They can also come together to do a powerful attack on all enemies. For thier overdrive, Delta Attack, all three of the sister's overdrive bars must be full.

Location: Remiem Temple
Capture all the monsters in the Mount Gagazet area and return to the monster arena to recieve the Blossom Crown. Then go to the Remiem Temple, making sure you have all the Aeons including Yojimbo and Anima (to get to the temple you need to have trained a chocobo in the Calm Lands, then go to the entrance to the Calm Lands and you will see a Chocobo Feather examine it to jump down to the entrace to the temple). Enter the temple and you will see Belgemine, defeat all her versions of the Aeons (after beating Bahamunt you obtain the Flower Scepter). Head over to the door at the back of the temple and open the door.
Special Ability: Camisade, Razzia, Passado
Overdrive(s): Delta Attack
How to Break Damage Limit: Not needed.