[Ducky]

Commander is a 100 card format, where you're only allowed one of each card (bar basic lands) and you build it around your commander who is in his own special zone, rather than your library, where he can be summoned from as soon as you have the required mana. Then every time the commander dies it will return to its commander zone, and will cost an additional 2 to cast.
you get 40 life each, but 21 damage from a single commander will kill you.