What is Commander?
Commander, also known as Elder Dragon Highlander or EDH, is stated as a casual multiplayer format for Magic: the Gathering. It is a 40 life, 100 card singleton format or a Highlander-variant format with specific rules centered around a legendary creature called the Commander.
Deck Construction.
You select your Commander from the legal choices of Legendary Creatures or Planeswalkers that have the stated ability that they can be your Commander. There are some cards with the Partner mechanic, a special ability that allow you to have two commanders with the Partner mechanic or Partnered with another specific Legendary.
Blind Obedience is White.
Construction of the deck is based around your Commander’s colour identity. This identity is determined by the mana cost and any mana symbols that appear in their rules text. The cards within the deck must comply to your Commander’s colour identity and not include any other colours. However, this does not include any listed reminder text that may appear in the card’s text.
The deck must consist of exactly 100 cards including your Commander. As a singleton format that means that besides the 5 basic lands you can only have one copy of any card in your deck. Commander also does not support “Wish” cards as there is no Sideboard in the format barring any “House Rules” to allow the cards to function.
The Banlist for the Commander Format is determined and maintained by the Commander Rules Committee rather than Wizards of the Coast themselves. This list of banned cards as well as historical changes to the list and philosophy of the Commander Format can be found on their website mtgcommander.net. Wizards of the Coast also has a page on their own website for the Commander format.
Game Play.
To begin the game, you start at 40 life with your Commander in the Command Zone. Aside from that, it follows the normal rules for Magic. Shuffle your deck, offer your deck to your opponent(s) to cut, determine who goes first, and resolve Mulligans. In a multiplayer game, the player going first will also get to draw on their first turn. Turns are taken in a clockwise order (player to the left takes the next turn).
Commander Specific Comprehensive Rules.
There is a specific section in the Comprehensive Rules document of Magic that only apply to the Commander format. This section can be found under Comp Rules 903. Commander. Below are a few of the most relevant rules you will need to know.
Commander Tax 903.8
A player may cast a commander they own from the command zone. A commander cast from the command zone costs an additional {2} for each previous time the player casting it has cast it from the command zone that game. This additional cost is informally known as the “commander tax.”
Commander Zone Change 903.9.
If a commander would be exiled from anywhere or put into its owner’s hand, graveyard, or library from anywhere, its owner may put it into the command zone instead. This replacement effect may apply more than once to the same event. This is an exception to rule 614.5.
Commander Damage 903.10a.
A player that’s been dealt 21 or more combat damage by the same commander over the course of the game loses the game. (This is a state-based action. See rule 704.
Have fun, and welcome to Commander.