In the first Star Ocean, the only arena available is the Tatroi Arena from the Astralian town of Tatroi, on Roak. There, Roddick or his friends can face various enemies from dungeons of Roak and Fargett in sets of four one-on-one battles. The enemies change according to the rank enlisted in (Which varies from Rank H to Rank A) and the character itself (depending on if it is a magic-using character or a melee character).
Ashlay Bernbeldt's and T’nique Arcana's recruitments involve the participation in the Tatroi arena as well. For the first, you must complete any rank once, and for the second, you must face him in Rank D.
The second Star Ocean is special in terms of arenas as there are actually two arenas in the game, although one is available for story purposes only, the Lacour Colosseum. On the other hand, the arena of the NedianFun City works in a similar way as the Tatroi Arena, but is more complex. Team battles and solo battles are available as well as a survival mode where 50 enemies are fought consecutively. There are not as many ranks to fight in (Only Rank E to Rank A are available). It costs 2000 Fol to participate in any of these battles, but this cost is countered by Fol recieved in battles. Sets of items are available as prizes.
Like in the original Star Ocean, the arena available is the Tatroi Colosseum in Tatroi, on Roak. It is used for both storyline purposes and is available after storyline events in the Purgatorium. It functions in a similar manner to the second Star Ocean's arena, with various differences.
Ashlay Bernbeldt can be fought as the top-ranked opponent in Team Battle, and there are plenty of Battle Trophies to be won involving the Colosseum.