First of all, you need every Aeons in the game including Anima and Yojimbo. Once you have that, you are ready to go on with the Sidequest. First, head to Mt. Gagazet and capture every fiends there, there is a total of eleven fiends, look in the Monster Arena Section for a list of the fiends you can capture. Next, return to the Monster Arena owner in Calm Lands and he will reward you with the Blossom Crown. Then, go to Remiem Temple in Calm Lands and fight Belgemine. Since you probably have defeated her Valefor already, defeat her Ifrit for now. Here’s the list of the prizes you win by defeating her.
|Valefor||Aeon’s Soul, Power Sphere (x30)|
|Ixion||Chocobo Feather (X10)|
|Yojimbo||Shadow Gem (X8)|
|Anima||Stamina Spring (X60)|
|Magus Sisters||Shining Gem (X40), Moon Sigil|
Once you have defeated her Bahamut, you will have the Flower Scepter. Use both items on the north door and acquire the Magus Sisters. Now, return to speak to Belgemine and fight her own Magus Sisters to complete this Sidequest. After you have defeated her, you will get the Moon Sigil and you will also learn that Belgemine is an unsent. You can send her if you want, then this Sidequest is in the books!