2v2 teams and multiplayer games

Every mode of play fills in the same blanks: how many players, how they are organized, the Victory Score, the battlefield count, setup, and the first-turn process (rule 485). Learn the blanks, then learn what 2v2 adds.

The modes. The 1v1 modes, Duel and Match, have 2 players, a Victory Score of 8 and 2 battlefields, one from each player. The player going second channels an extra rune on their first turn (rule 487 and rule 488). FFA3 (Skirmish) has 3 players and FFA4 (War) has 4, each with 3 battlefields and a Victory Score of 8 (rule 489 and rule 490). In FFA4 the player taking the first turn removes their battlefields (rule 490.4.b). In both free-for-alls the first player does not draw in their first Draw Phase and the last player channels an extra rune (rule 489.7 and rule 490.7). 2v2 (Magma Chamber) has 4 players, two teams, 3 battlefields and a Victory Score of 11, with the same first-turn process, and the first player removes their battlefields (rule 491.1, rule 491.3, rule 491.4, rule 491.5.b and rule 491.7).

Worked example, 2v2. It is your Main Phase and you are the Turn Player. Your teammate holds Twilight Shroud, a spell with neither Action nor Reaction, and wants to use it now. Only the Turn Player can normally play spells in a Neutral Open State, but in modes with teammates your teammate may play spells and activate abilities, even without Action or Reaction, when you invite them using your own Priority (rule 316.5.b.1 and rule 491.8.a). The spell says "Give a friendly unit +1 Might this turn", and friendly includes your teammate's units, so it can pick a unit of either of you (rule 491.8.e and rule 740.1.a).

Teams. Teammates win or lose together: if one player concedes, loses or wins, so does the team (rule 491.6.a). Points are shared, and a spell that checks a player gaining points checks their team (rule 491.8.d.1, rule 491.8.d.2 and rule 491.8.d.3). Control is not shared: a player can't hide cards at a teammate's battlefield or give a teammate's units a standard move (rule 491.8.c.1 and rule 491.8.c.2). A battlefield scores only once per team per turn, and one a teammate controlled during the Scoring Step of your Beginning Phase can't be scored by your team that turn (rule 491.8.b and rule 491.8.b.1). The Final Point from a Conquer needs every battlefield scored that turn, except those your ally occupied during that Scoring Step (rule 491.8.g.1). Teammates may not share a Champion Legend or battlefields (rule 491.8.h and rule 491.8.i). Turn order alternates teams (rule 491.5.c).

Combat with more than two players. Combat can only happen between units controlled by exactly two players (rule 464). In modes with more than two players, a battlefield with a staged combat or one in progress is an invalid destination for moves by units of players not involved in that combat or who don't already have units there (rule 464.1). Those players also can't choose it as a location to play a unit, and the unit is played to their base instead (rule 464.2 and rule 464.2.a). Any choice that would produce a combat between more than two players at once is invalid (rule 464.3). Battlefields a teammate occupies are invalid move destinations too (rule 449.2.b).

Tournaments. Teammates register as an A and a B player and sit next to each other. Turns go first team's A, second team's A, first team's B, second team's B (TR 603.7 and TR 603.7.a). A random method picks which team chooses the starting player, and that team chooses where in that order play begins, and after game one the team that lost the previous game chooses who plays first, keeping the previous order after a draw (TR 603.7.b, TR 603.7.c and TR 603.7.c.1). If a player drops or is disqualified, so is their team (TR 603.3 and TR 603.4). In 2v2 teammates may share private information, though in other games players need not share it and may bluff (TR 502.12 and TR 502.11).

Common mistake. "My teammate and I can act for each other any time." Only when invited on your own Priority, and control of battlefields is not shared.