To battle against other players in The Arena you must obtain a Battlepack from the ComPet Shop. Basic Battlepacks are exchanged for Gold, whilst Premium Battlepacks are exchanged for real-cash virtual currency (Project Entropia Dollars/PED). The winner of the battle gets part of the value of the loser’s Battlepack.
If you want to know more about battling in ComPet, please see the “#5 Battle” post.
Here is the range of Battlepacks currently available in the ComPet Shop:
Basic Battlepacks:
Premium Battlepacks: