Arena Mode (アリーナモード Arīna Mōdo) is a feature that appears in Kingdom Hearts Birth by Sleep. It serves a similar purpose as the Olympus Coliseum cups, allowing players to fight a series of set matches against enemies. It can be played either as a one-player mode or as a multiplayer mode over a wireless connection with up to six participants. As with other events occurring in the Mirage Arena, players appear as Terra, Ventus, or Aqua, wearing their Keyblade Armor, rather than their usual gameplay attire.
The names of who is playing with you appear above their respective character, and while fighting their HP are displayed like someone who is in your party.
Gameplay
In a new world called the Mirage Arena, three players can access and engage in battles for cooperative play. The Mirage Arena is a world exclusive to Arena Mode.
Through this multiplayer mode, items and other bonuses can be transferred between single and multiplayer modes. Unique elements of battle include rescuing friends trapped by the Unversed, and continuously pressing the 
button to heal fallen players. Players may customize their displayed name and the color of their armor. At the end of a completed playing session, winning medals are distributed on a results screen.
The faceshot of Terra, Ven, and Aqua seen in the HP bar is of their helmets. A rating system also appears, showing a level of who stands in what place by displaying differently colored symbols.
Matches
- Day of Reckoning - Rank 1
- Wheels of Misfortune - Rank 1
- Weaver Fever - Rank 2
- Sinister Sentinel - Rank 2
- Dead Ringer - Rank 2
- Combined Threat - Rank 3
- Risky Riches - Rank 1
- Harsh Punishment - Rank 3
- A Time to Chill - Rank 4
- Treasure Tussle - Rank 3
- Copycat Crisis - Rank 4
- Keepers of the Arena - Rank 5
- Villains' Vendetta - Rank 5
Birth by Sleep Final Mix exclusives
Characters
- Terra armor.png
Power Type (鎧の青年 Yoroi no Seinen, Armored Youth)
- Ven armor.png
Speed Type (鎧の少年 Yoroi no Shōnen, Armored Boy)
- Aqua armor.png
Magic Type (鎧の少女 Yoroi no Shōjo, Armored Maiden)
Gallery
- Joint struggle2.jpg
A player reviving an ally during an Arena match
- Joint Trinity.png
The Trinity Limit ability being used in an Arena match
- Mirage Lobby.png
The Lobby, where teams and other Arena Mode customizations are selected