Colosseum
The Colosseum, also known as the Arena, is a game mechanic that first appeared in Hyperdimension Neptunia mk2. The Colosseum allows the party to engage in special battles for prizes, without incurring a Game Over in the event of defeat.
Overview
The Colosseum offers various battles, all categorized by rank. As the party enters a battle, they will be greeted by enemies that they must defeat. If all enemies are defeated, they are rewarded with credits and special prizes for winning the battle.
Clearing each battle will also affect each nation's shares (e.g. Planeptune gains 10% of shares while Lastation loses 10% of shares and vice versa).
In Hyperdimension Neptunia Re;Birth1, if one has the Survival Mode DLC installed, the Colosseum battles are split into various rounds.
A similar mechanic known as the Arena is first featured in Neptunia: Sisters vs Sisters where the battles use a three-round system similar to Re;Birth1, and the player can go into training by choosing enemies with the amount appearing and AI behavior specified.