You'll get prizes when you return to the owner with the required creatures. Some of them are extremely rare. In addition, you can also fight unique creatures that the owner creates from captured fiends. Prizes are awarded each time you accomplish one of the following:

CAPTURE ONE OF EVERY FIEND IN EVERY AREA.
CAPTURE 10 OF EVERY FIEND OF A SPECIFIC SPECIES.
CAPTURE 10 OF EVERY FIEND IN EVERY AREA.

Complete a total of 10 either Species Conquest or Area Conquest for the Mars Sigil, which unlocks the potential of Auron's legendary weapon.

While backtracking in the game and lookinf for the spheres that trigger Auron's Overdrives, equip Capture weapons and collect fiends from each area you have to visit. To see where these spheres are located, check Auron's section of the characters chapter, "A Summoner and Her Guardians."

The owners weapons are expensive, so buy weapons for character who you know can take down a lot of HP in one hit. This will most likely be Wakka, Auron, Tidus, or perhaps Kimahri.

After capturing fiends, you can pay to fight them in the arena. What's the point when you've already fought these monsters elsewhere? When fighting monsters here, you can steal better items, win spheres for the Sphere Grid, and you can bribe them for rare items!

Currently under development. Sorry for the inconvience.