Bo is short for "best of" and the number refers to the maximum amount of games that will be played. A player wins any best of match as soon as he/she wins more games than half the number of maximum games. Possible results e.g. for a Bo3 are 2-1 and 2-0 and for Bo5 are 3-2, 3-1, 3-0. Usually, the winner keeps their deck and the loser has to pick a new one.
Within a bracket, a player compete against an opponent who has won the same amount of matches until they lose a match. Each match except for the first round, where everybody is assigned randomly, consists of two players who won a preceding match. Thus, half of the players each round are eliminated until only one player, the winner of the bracket, is left. Brackets are used with the formats 2.1 Single Elimination and 2.2 Double Elimination.
Seeding refers to the process that determines the pairings of a tournaments first round. Usually, it's randomized but pairings can also be created according to previous qualifier (3.2) results.
1.4 Free win
If an unequal number of players is competing within a bracket (1.2), players who don't have an opponent in the first round get a free win and proceed to the next round without playing a match. This also applies if an opponent doesn't show up or resigns from the tournament.
A ban allows a player to remove one of their opponent's classes from their set of possible decks before the match starts. A variation of this is the coup used in the Pinnacle tournaments where a player can once decided to ban an opponent's deck by conceding during the mulligan phase.
1.6 Group stage
Players are divided in groups of the same size and compete according to the round robin format (2.4) against each other. Usually, half of the players from each group will advance to the playoffs (1.7).
Playoffs take place after a group stage (1.6) and are usually played as a single elimination bracket (2.1).
A league is played over a certain period of time and usually uses the round robin system (2.4).
1.9 Arena Draft
Arena tournaments use arena drafted decks instead of constructed ones. Usually, players will draft an arena deck and recreate it with their own cards like a constructed deck. It is not allowed to draft a card three times or more as it is not possible to have more than two copies of one card in a constructed deck.
In a single elimination tournament, players are competing within only one bracket (see 1.2). In every round, half of the players are eliminated due to losing their matches and once eliminated, they do not longer participate in the tournament.
2.2 Double Elimination
A double elimination tournament uses two brackets (1.2) instead of only one like the single elimination (2.1). The second bracket is also known as the loser's bracket. This means that a player who loses their first game will be added to the loser's bracket in the corresponding round. The winner of the loser's bracket will be the second finalist.
Players play against each other over a predetermined amount of rounds and the player with the most wins or highest score after the last round wins the tournament. The first round's opponents are randomly assigned whereas opponents of later rounds are matched according to their previous results, e.g. the leading player competes against the best other player he has not played against yet. This ensures that players play against an opponent with equal skill without anybody playing against the same opponent twice.
2.4 Round Robin or All-play-all
Everybody plays against each other player. This can also be played as double round-robins where everybody plays twice against each other. Usually, this system is used for leagues (1.8) or within groups (1.6) as this format as only tournament format would require a lot of time for high player numbers. In theory, this system provides the most accurate or fair results.
2.5 King of the Hill
The winner of the previous torunament competes against a challenger who will become the new king of the hill if victorious. Otherwise, the old king of the hill has to be challenged again and remains on their throne until beaten.
The conquest mode is similar to a regular Bo5 (1.1) with the only difference that the winner must change their deck whereas the loser is free to keep or change theirs. Once a player has won a game with a certain deck, he/she can't use it again.
Open tournaments can be joined by everyone who has an account on the region where the tournament takes place.
For certain tournaments players must qualify in order to be allowed to participate. Qualifier tournaments are usually open to everyone and precede tournaments with higher prize pools and/or invited players.
Players for this kind of tournaments are invited by the host because of to their performance in earlier tournaments or general reputation.
3.4 Paid Entry
Players pay a fee to participate in the tournament. Usually, the entry fees of all players are added up and are used as the prize money.
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