Decks have one Commander, generally a legendary creature or card with the ability that allows the card to be used as a Commander. Decks may contain only cards from the chosen Commander's color identity. Players start with 40 life rather than the usual 20. See this page for comprehensive rules.
Great for casual group play.
100 cards (1 Commander and 99 others)
No more than one of any individual card in the deck (with the exception of basic lands).
See this page for a list banned cards.