Arena Standard also known as Best-of-one (or Bo1) is a Magic Arena-specific constructed format of Magic: The Gathering.
In Best-of-one, players submit a Standard–legal deck for play with no necessity of sideboard. A match consists of only one game, instead of the usual three (Bo3). Cards like Mastermind's Acquisition find still only cards in a player's sideboard rather than their full in-game collection.
Because losing a single-game match after a mulligan feels worse than normal without the fallback plan of winning the other two games, starting hands are randomized in a way that should reduce the frequency of mulligans, but without incentivizing mana base construction outside the strategic norms of the game. Wizards feel this achieves the desired effect of reducing the frequency of mulligans without changing how players build their mana bases.
- The system draws an opening hand from each of two separately randomized copies of the decks, and leans towards giving the player the hand with the mix of spells and lands (without regard for color) closest to average for that deck.
- The "closest to average" usually means three lands in starting hand because 22÷60×7≈2.567 and 28÷60×7≈3.267.
- You can then use standard Vancouver Mulligan rules to get a new hand with one fewer card. Mulliganed hands are created from a single randomized draw.
In addition to the traditional Standard ban list Nexus of Fate was banned as well.