From Liquipedia Hearthstone Wiki
"Conquest" is a kind of match format announced by Blizzard for using in 2015 Hearthstone World Championship.
- All matches will be best-of-5. The first player to win 3 games within the match is considered the winner of the match and advances.
- Each player must submit decklists from three unique classes prior to each stage of the event. Players may submit new decks prior to each stage of the event.
- A player must win one game with each of his three decks to win the match.
- When a player wins a game, the deck used by the winning player cannot be used for the remainder of the match.
- The losing player can keep the same deck used or switch to a different one of their choice.
- Players will be told what classes their opponent has available, but they won’t know which class is picked until both players have picked.