Star Ocean: Till The End Of Time

Team Battles in the Fighting Arena play out very similarly to the Single Battles, except you can bring your team with you making fights significantly easier. You fight virtually the same enemies you fought in Single, except in some cases there might be more of the same enemy. Still, the same rules and tips still apply. Below are the 5 ranks you need to beat and their rewards:

D Rank - Entry Fee: 100 Fol (Reward: Synthesis Materials)
C Rank - Entry Fee: 300 Fol (Reward: Tri-Emblum)
B Rank - Entry Fee: 500 Fol (Reward: Scumbag Slayer)
A Rank - Entry Fee: 1000 Fol (Reward: Star Splash)
S Rank - Entry Fee: 2000 Fol (Reward: Ring of Slaughter)

Make sure you have a dedicated healer in your party and these battles should prove little trouble. Once you've completed all 5 ranks, the trophy will unlock.