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It first appears in Mario Party 5 as a capsule that players can place on a space. Anyone who lands on a space containing the Duel Capsule chooses an opponent to duel with, then what the wager will be. However, players can also choose to put Stars on the line, whether it is for the opponent giving the winner a Star for 40 coins, or a Star for a Star. A similar space called the VS Space appears in Story Mode. If the Koopa Kid or the player lands on a VS Space, this triggers a 1 vs. 3 minigame. If the player wins, they get 5 coins from all 3 losing Koopa Kids (a total of 15 coins), but if they lose, they must give 5 coins to each of the winning Koopa Kids. If there are 2 Koopa Kids remaining, this triggers a 2 vs. 2 minigame, and the player gets Toad as their partner. If the player wins, they get 10 coins from both of the losing Koopa Kids (a total of 20 coins), but if they lose, they must give 10 coins to both of the winning Koopa Kids. If there is one Koopa Kid left, this causes a duel minigame. If the player wins, they get 20 coins from the losing Koopa Kid, but if they lose, they must give 20 coins to the winning Koopa Kid.
In Mario Party 6, Duel Spaces are already placed on the board, and landing on them has the same effect. The Duel Space in Mario Party 7 is different though; gameplay is the same, but instead of picking the stakes, the winner does an event where they hit a ! Block to stop the roulette. Whatever it shows, the loser gives coins to the winner (10, half, or all of their coins). If the winner lands on the "X", the loser will not give any coins to the winner. In Mario Party 8, the Duel Space is called the VS. Space, and is only found in Star Battle Arena. The player that lands on one plays a Minigame with their opponent. The loser of the duel gives coins to the winner via the dart wheel (also, the shape of the space is different with each board, including the tutorial). In Mario Party 8, the attacker (if they win) gets the dart wheel that has 5, 10, or 20 coins; while the defender (if they win) gets the dart wheel that has 1, 5, or 10 coins instead. In Mario Party DS, the Duel Spaces appear only after the Final 5 Frenzy, as a replacement of the Friend Spaces.
In some of these games, players get to decide whom to duel against. However, if a CPU player lands on this, they will usually challenge the player in first place (or second place if the player who landed on it is in first place) to duel them. Additionally, if the player lands on this space, hitting Random will usually select the CPU player in first place (or second place if the player is in first place).