The deckbuilding rulesets for Constructed do not apply to Arena; players can draft multiple copies of cards from any faction, and there is no provision limit. An Arena run is finished with 9 wins or 3 losses against other players, whichever comes first. Players collect a reward according to their performance, with 9 wins rewarding a legendary card. Entry into Arena is paid with real currency or ore.
To help you with drafting the best cards in Arena, check out our Arena Tier List and Card Picker.