The stage is a fairly small colosseum-like area. The fight starts with 2 Viking, 3 Energist, and Death Machine in the middle. All of the bandits are Dark element and have -10% resistance to Light and Slash. After 3 enemies are defeated, 4 more Viking bandits will show up.
Because the area is somewhat small, it can be easier to have the enemies focus their attacks on your tank by making them go forward first after some buffs, then start to whittle them down with the rest of your party. Make sure to stack up on some Slash and magic resistance to survive their attacks.