Commander is played, on average, with four people.
The decks are 100 cards (99 in the deck and 1 for the general). You are allowed, in the San Diego league, to use a maximum of 10 proxies. That’s great news to those of you who want to run expensive cards, like lands or creatures that are too expensive.
Your life total starts at 40.
The player who rolls the highest starts first. That person also draws a card. The turns proceed in a clockwise fashion.
The mulligan system in Commander works differently (at least in Southern California) from the other mulligans you might be used to. The mulligan is called partial paris. After you draw your hand, you may choose cards that you do not want, put those aside and draw that many. For example, if I draw 5 lands and 2 bombs like Terastodon and Myojin of Night’s Reach, i may put aside the two, draw two cards and then shuffle the two i set aside into the deck. After that, I can reassess my hand and mulligan the same way, but this time if I decide to pitch two cards, I can only draw one. So it’s basically a free mulligan the first time, but every time after the first its a cumulative -1 draw.
When your general dies, he costs an additional 2 colorless mana to play. For example, if I cast Wort, the Raidmother and she is placed back into the command zone, costs 6 + 2 additional. At the time your general would be destroyed you may opt to put him into the command zone OR the graveyard. If he were to become exiled, then you have no choice; you must put him into the command zone. Cards like Hinder or Bant Charm that may place the general in the deck do NOT give the owner the opportunity to put it into the command zone. If your general becomes placed under an Oblivion Ring like effect, you may choose to put him into the command zone or leave him exiled.
When a player dies, all permanents they own are removed from the game and their spells are removed from the stack. So, if someone steals your Primeval Titan and you kill them, you get it back! Granted it’s still on the field when they die.
If a player takes more than 21 points of general damage from a SINGLE general (including your own), that player loses the game.
The game continues until one person is left standing.