A Legendary Creature (or specific Planeswalkers) that starts in the Command Zone and can be played multiple times, costing an extra
generic mana each time it is recast from there.
Every card in your 100-card deck must match the color(s) of your commander's mana cost, including mana symbols in the rules text.
Only one copy of any card (except basic lands) is allowed per deck.
Players start with 40 life instead of 20.
If a player takes 21 points of combat damage from a single opponent's commander over the course of the game, that player loses!!!