Your Deck:
1 commander card (any legendary creature (or planeswalker if it says it can be your commander))
1 talisman card (any non-creature, non-land artifact)
78 other cards
Only one copy of any card, except for basic lands
The color identity of all cards in your deck, including your talisman (and companion, if used), must fall within the color identity of your commander (color identity encompasses colored mana symbols in both the card's cost and its rules text—for example, Shalai, Voice of Plenty's color identity is green-white).
Exception: if your commander is colorless, you can play unlimited copies of any one type of basic land.
The Game:
2–6 players
Take turns in clockwise order.
Start at 30 life.
The first mulligan is to seven cards, then each mulligan afterward results in one fewer card (six, five, four etc.)
All commanders and talismans start in their command zone
Commanders can be cast for their mana cost, plus 2 mana more for each time it's been put back in the command zone
Talismans stay outside the command zone after you cast it, unless for some reason a card specifically states to put it into the command zone, meaning they can leave the battlefield without you choosing to put it back into the command zone. This is similar to the old rules for companion, before you had to pay 3 to put it in your hand.
Last player standing wins
Other Rules:
No commander damage is used.
No sideboards are used.
Abilities which bring other card(s) you own from outside the game into the game (such as Living Wish; Spawnsire of Ulamog; Karn, the Great Creator) do not function in Commander, except for companion cards. If you have a companion card, it is not in your sideboard, nor is it outside the game. It is simply off to the side and you can pay 3 mana to put it into your hand. Both your commander, talisman, and all cards in your deck are required to have the deck restriction of your companion.