I've been tapped by Trick to write a primer on Elder Dragon Highlander (EDH) Commander and I'm pretty excited. I'll delve into the game play aspects another time, but first I want to quickly skim over the rules and philosophy of this great format.
While there are a set of rules that have been set forth for league play I'm going to cover the more casual aspects for right now and leave the league to a different day.
Deck Construction:
Your deck for EDH Commander needs to be 100 unique cards (excluding basic lands.) In order to construct your deck you first need to choose a General Commander.
Your General Commander must be a legendary creature and the mana symbols in their mana cost will govern how you build your deck, but more on that in a second. Though most legendary creatures are perfectly fine for selection there are a few no-nos.
Memnarch and Bosh, Iron Golem both violate some of the rules for deck construction and as such are unfortunately not allowed. The reason Memnarch and Bosh are illegal is because the mana symbols in your general's mana cost are the only mana symbols which can be played anywhere in your deck. Both Memnarch and Bosh have no colored mana symbols in their costs but they do have colored mana symbols in their textboxes they break their own rules. A deck's color identity is determined by the mana symbols present in the casting cost, and rules text of a card. So your deck can be composed of any color on your legendary creature commander. You might also avoid Braids, Cabal Minion for the social aspect alone.
It's also worth noting that, no matter how much we want them to be, Planeswalkers are not creatures, nor even are they legendary (though their rules mimic the Legendary rule in some ways) and as such are not allowed as Generals Commanders.
There are a few more points to take into consideration. Hybrid mana symbols need to both appear in your commander's mana cost. So if I'm using Eladamri, Lord of Leaves as my Commander, I can't have Selesnya Guildmage coming to hang out. Also, the Onslaught cycle of "fetch lands" and lands similar in nature don't have a mana symbol, they name the cards searchable. So it's perfectly acceptable to run Bloodstained Mire in your Maga, Traitor to Mortals deck (in case you want multiple ways to find that Leechridden Swamp!). As far as deck construction goes that's it!
Well, almost. You want to try to keep your card selection to things that are legal in vintage though there is an exception, Shahrazad is perfectly legal, though no less frustrating.
Starting the Game
Now that we can build our EDH Commander deck let's talk about a few of the nuts and bolts aspects of actually shuffling up. The first thing you need to do when you sit down is announce your General Commander and pull them out of your deck into the 'command zone.'
The command zone is a separate zone where your General Commander likes to lounge whenever he's not in play. One version of this I've found to be very helpful is to put the four (or more) generals in the center of the table in a corner to corner fashion, sort of like you're summoning Captain Planet in card form.
Each player then draws their opening hand and gets to take any mulligans. Mulligan is a four letter word in tournament magic, but in EDH Commander it's really not so bad. Commander's official mulligan is the "partial paris" mulligan. Each player may exile any number of cards from their hand face down and then draw one fewer than they exiled. This simulates a mulligan without the randomness of potentially losing all your lands.
The exiled cards are then shuffled back into the library. There is also another form of mulligan used in my local playgroup, the "Gis" mulligan, named after former L5 super-judge Gijsbert Hoogendijk. The Gis mulligan requires each player to exile their hand face down and then draw a new hand of seven. Each player may repeat this as many times as necessary and then the exiled cards are shuffled back in. To prevent rampant abuse our group has a gentleman's rule where if you have 3 or more lands in your hand you cannot Gis mulligan.
Game Play
Fantastic! Now it's game time, and I can practically hear Mills Lane growl "Let's get it on!" But unfortunately we have a few more things to learn first.
Generals Commanders can kill players all on their own, just by dealing 21 points of combat damage. That can be an important fact, because each player is going to start at 40 life rather than the normal 20. It's also normal to see some pretty wild life totals in EDH Commander.
In addition, your General Commander has a few other special things about him/her/it/whatever-gender-dragons-have. Your General Commander has a special property of "Generalness." It can't be overwritten or lost. So if I manage to turn your General Commander face down, or make it into a copy of a different creature (hello Mirrorweave!) then the damage your General Commander is doing still counts toward those 21 points.
Generalness cannot be copied, so that Clone you have that's copying my
Speaking of Clone, though your general is neat and unique it is not immune to the legend rule. Clones, shapeshifters, and just plain having someone cast their own copy will all kill your General Commander if it's on the battlefield.
This brings up an important point, how exactly does your General Commander get into the battlefield? When you cast it! You can cast your General Commander anytime you have the mana and you would normally be able to cast that spell. Teferi as your General Commander? Sure, flash him in at the end step!
Now there is a little something extra about your General Commander, when it dies you get to decide where it goes. If your General Commander would be put into a graveyard from anywhere instead it can go back to that command zone, ready to fight another day. If you'd rather have your General Commander go to the graveyard that's fine too, but probably a little less relaxing. I always like to have a few saucy looking cards in the command zone for my General Commander to relax with. Lady of proper etiquette? She's definitely a stern taskmaster.
Unfortunately for us there's a small catch about your General Commander being recast. Each time it goes to the command zone it's a little less happy about coming back. So much so that you need to pay two more mana for each time it's been cast this game. So if Venser is your General Commander he'll happily keep bouncing things when you cast him, just for the second time, and , the third, and so on.
And with that it about covers all the wacky differences between EDH Commander and a regular game play-wise. There are a few other things to consider.
Wrap-up
EDH Commander is meant to be a casual and socially friendly format. When you sit down at a table for a game of EDH Commander be sure to leave your inner Spike at home and have a little fun. I've participated in games where Eternal Dominion has been copied by Hive Mind, Kresh the Bloodbraided has been flung at someone for well over a hundred points of damage, and there have been 12+ copies of Blood Tyrant on the table.
When you play EDH Commander the goal is for everyone to observe a social contract and have a good time. It's very easy to assemble a broken combo very quickly when every tutor in magic history is available and no one is hyper aggressive. If someone is ruining the fun of your group's experience, do not be afraid to let social pressure handle the situation. One of the easiest ways I've found is to simply say "good job, you've won, we're going to play for second place."
It turns out winning on turn 1 isn't quite as fun when you're sitting watching everyone else have fun for the next 2 hours. There are so many more things I want to say about this format, and I will in upcoming weeks, but for now I think I'm going to leave you with a sample decklist. Don't let the card types/prices concern you, my deck was built over time, picking up cards piece by piece until I found what I really liked. I plan on taking a look at some budget options that let everyone have fun for a fraction of the cost of this monstrosity.
[cardlist]
[Red]
1 Chandra Nalaar
1 Incendiary Command
1 Obliterate
1 Wild Research
[/Red]
[White]
1 Elspeth, Knight Errant
1 Enlightened Tutor
1 Idyllic Tutor
1 Wrath of God
[/White]
[Blue]
1 Bribery
1 Intuition
1 Jace Beleren
1 Mystical Tutor
1 Telemin Performance
1 Tezzeret the Seeker
[/Blue]
[Black]
1 Beseech the Queen
1 Cruel Tutor
1 Damnation
1 Demonic Tutor
1 Diabolic Tutor
1 Lilianna Vess
1 Tainted Pact
1 Tsabo's Decree
1 Vampiric Tutor
[/Black]
[Green]
1 All Suns' Dawn
1 Farseek
1 Gaea's Blessing
1 Garruk Wildspeaker
1 Harmonize
1 Kodama's Reach
1 Krosan Grip
1 Mwonvuli Acid-Moss
1 Nature's Lore
1 Nature's Spiral
1 Rampant Growth
1 Regrowth
1 Restock
[/Green]
[Artifacts]
1 Coalition Relic
1 Coldsteel Heart
1 Mana Crypt
1 Mana Vault
1 Mindslaver
1 Mindstone
1 Proteus Staff
1 Rings of Brighthearth
1 Sol Ring
1 Sensei's Divining Top
[/Artifacts]
[Gold]
1 Ajani Vengeant
1 Bituminous Blast
1 Cerebral Vortex
1 Maelstrom Nexus
1 Nicol Bolas, Planeswalker
1 Pernicious Deed
1 Putrefy
1 Sarkhan Vol
1 Sterling Grove
1 Vindicate
1 Void
[/Gold]
[Lands - A-P]
1 Academy Ruins
1 Ancient Tomb
1 Badlands
1 Bayou
1 Blood Crypt
1 Bloodstained Mire
1 Breeding Pool
1 Flooded Strand
1 Forest
1 Godless Shrine
1 Hallowed Fountain
1 Island
1 Jungle Shrine
1 Krosan Verge
1 Maze of Ith
1 Mountain
1 Overgrown Tomb
1 Plains
1 Plateau
1 Polluted Delta
[/Lands A-P]
[Lands R-Z]
1 Reflecting Pool
1 Sacred Foundry
1 Savage Lands
1 Savannah
1 Scrubland
1 Seaside Citadel
1 Steam Vents
1 Stomping Ground
1 Swamp
1 Taiga
1 Temple Garden
1 Temple of the False God
1 Tropical Island
1 Tundra
1 Underground Sea
1 Vesuva
1 Vivid Grove
1 Vivid Meadow
1 Volcanic Island
1 Watery Grave
1 Windswept Heath
1 Wooded Foothills
[/Lands R-Z]
[/cardlist]