Colosseum Coin

Coin Rewards by Room
To complete a stage, use the door exiting that room. For example, if you have cleared all the spawns in room 15 and use the door to get to room 16 you would get 2 coins for completing 15. If you die and reenter and get portaled before you reach the group, you will get the rewards corresponding to the last door you went through.

Other

 * You can also get 2 coins from turning in a Colosseum Ring to the Master Arbitrator, along with 140 million xp. The rings are Ivoryable and can be turned in on other characters.
 * During Risks and Rewards the Casinos had a Grand Casino Chest added that sometimes gives a Colosseum Coin.
 * The following seasonal quests have colosseum coins as possible rewards :
 * Hidden Presents
 * Reception Games