Note: Information on this page is inaccurate, misleading and out-of-date.
The auction house is a feature where players can either put their cards up for sale or bid on cards that other players have put up for sale. Both selling and bidding on cards requires spending non-refundable auction tokens. If a player puts a card up for sale and no one bids the card is returned but the tokens are not. Likewise if a player bids on a card but is outbid by another player gold is refunded but tokens are not.
To sell a card players must spend a set amount of auction tokens which varies depending on the rarity of the card being sold; 1 token for an uncommon or rare card, 3 tokens for an epic, and 5 tokens for a legendary. Players can also set an initial price for cards which varies depending on the rarity of the card being sold. Legendary cards can range from 500-1500 gold, epics 250-750, rares 200-400, and uncommons 50-250. Once put up for sale a card can be bid on by anyone for 5 hours.
To bid on a card players must have at least as much gold as the current maximum bid plus one auction token. Gold is immediately deducted from the player's account (this prevents players from spending more gold than they have) and is only permanently deducted if the player wins the card. There are two primary phases of bidding. First there is the 5-hour initial round where anyone can bid on a card. The first player to bid on a card pays the card's initial offer price in gold plus one token and is set as the leader of the round. If another player wishes to bid on the card, the player must pay the initial offer price +10 gold and one token, and is set as the leader for the round. This process continues for any number of players until the initial 5-hour round is over.
After the initial 5-hour open bidding round, any players who bid on the card enter a second 5-minute "knockout" round. Only players who bid in the first round are eligible to bid in the knockout round. Whoever was the last to bid in the initial round of bidding is the initial leader of the knockout round, and if no one bids that player wins. Otherwise bidding continues the same as in the initial round until the 5 minutes is up. After the first knockout round, any players who bid in the first knockout round enter a second 30-second knockout round which is the same as the first. Typically by the second knockout round a winner is decided as players run out of tokens to continue bidding with, however so long as at least two players bid there will be additional 30-second knockout rounds until a winner is determined.