Unite Against the Tyrant

This card starts face down in the command zone, reveal it only whenever you could cast a sorcery.
When this card is revealed, choose an opponent.
If that player has the most life among all players
and has a dominating board state, that player
gains 20 life and draws a card. Each other player becomes your teammate for the rest of the game.
(You share your combined life total and take simultaneous turns for the rest of the game)
End the turn.