You may have one companion in the Commander variant. Your deck, including your commander, must meet its companion requirement. Your companion is not one of your one hundred cards.
Your companion begins the game outside the game. In tournament play, this means your sideboard. In casual play, it's simply a card you own that's not in your starting deck.
9. Casual Variants
900. General
901. Planechase
902. Vanguard
903. Commander
=> selon les règles officielles, Commander est une variante Casual, en casual, tu prends la carte que tu veux qui n'est pas déjà dans les 100 cartes de base, et pour laquelle la règle de construction de deck est respectée.
=> j'imagine qu'une règle "officielle non-officielle" (càd, du comité "1vs1 20HP FDC") va venir, pour expliquer que bah non, c'est évident, on ne joue pas en Casual, donc ça vient de la réserve, donc on a maintenant le droit à une réserve d'une carte.
=> et, il faudra donc, j'imagine, une règle supplémentaire pour venir dire que "bah non, si on a mis un compagnon en réserve et qu'on a choisi de ne pas le révéler, on ne pourra pas aller le chercher sur Living Wish". Ou un truc un peu moins tordu, mais il faudra bien.
In a Commander game, each player puts their commander from their deck face up into the command zone after having the opportunity to reveal a card with a companion ability and before shuffling. See rule
903.6.
If a player is allowed to bring a card from outside the game into a Commander game, that player can't bring a card into the game this way if it has the same name as a card that player had in their starting deck, if it has the same name as a card that the player has already brought into the game, or if any color in its color identity isn't in the color identity of the player's commander.