Get the indicated rank at the Monster Arena to get the corresponding award:

Bardiche Of Binding: Rank B
Bunny Suit: Rank F
Dragon Robe: Rank S
Hero Spear: Rank A
Hero Statue: Rank S
Mighty Armlet: Rank D
Ring Of Clarity: Rank E
Saint's Ashes: Rank C
Strength Ring: Rank G
Call team ability for hero: Rank E
Fight against your team option: Rank F
No entry fees: Rank S
Second monster team: Rank B
Three more reserve monster slots: Rank D
Three more reserve monster slots: Rank G