Command Structure is a card type used by all four races:

Command structures must be protected at all costs, because if a player does not have any command structures at the end of a turn, that player loses the game. Other than this constraint, command structures function the same way as any other structure. If a card or rule mentions the word "structure", you should assume it applies to command structures as well.

Each command structure also provides an important role for that race's deck:

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