Command From the Shadows is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

(Start the game with this conspiracy face up in the command zone.) Players play with each of their commanders face down and secret until they cast them for the first time. (Be sure to tell your opponent you're using this right at the beginning of the game, so they don't reveal their commanders to you yet!)