The Commander format uses decks with exactly 100 cards (as opposed to the usual minimum-of-60), and it's a singleton format. That means you can only have one of each non-basic land card in the deck (as opposed to the usual limit of four). Each deck must have a "commander" legendary creature, and all the other cards in the deck have to share at least one of the commander's colors. You can use cards from the older sets, and very few cards are banned. Each player starts at 40 life (instead of 20), so quick damage isn't very reliable, allowing for more long-term strategies.
I really like the Commander format. It's tailor-made for a collection like mine: a bunch of cards from many different sets, usually with less than four of any particular card (especially rares). I can use my old cards which wouldn't be legal in a Standard or even Modern format event, and there's no disadvantage to having only one of a particular card. The commander-color restrictions encourage theme decks, which is one of my favorite things to do in deck construction anyhow. And the format is often played multiplayer, which adds some extra strategy (and chaos) to the way you play the game out.
My current favorite Commander deck is Gorgon themed. I used Sisters of the Stone Death as my original commander, though I've recently switched to Pharika, God of Affliction since it's much cheaper to play. Still fits the theme, though, which is lots of creatures with deathtouch, snakes, hydras, and of course gorgons. I even have a Gorgon life counter to go with it, from back in the Ravnica block days. The hydras are a bit of a stretch, but I ran out of gorgons and snakes to use, and I figure it's close enough. It's pretty terrible in a one-on-one matchup, but works great in multiplayer since no one wants to attack the guy with a bunch of poisonous snakes just waiting to kill anything sent their way.
The format has its drawbacks, of course. Most games take a long time to finish, particularly if there are more than four players. Shuffling your hundred-card deck can be a challenge, and you tend to do it often. Some commanders are a lot more powerful than others. The singleton format means you can't rely on drawing a particular card to disrupt the other players. And that can be a really bad thing when one player gets some kind of combo going.
Most of those issues are mitigated if you're playing with a good group of folks, though. Playing a long time isn't a big deal with good people. Super-powerful decks tend to be used once and then never again, since no one is interested in playing once they see it pop up again. And in multi-player, the chances are pretty good at least one person will be able to disrupt whatever crazy combo you're trying to pull off.
It's nice to play a format of MTG that doesn't require buying a whole bunch of new cards, lets me use my old stuff, and works well for multiplayer. And also tends to attract players looking more for an interesting game than just a quick win. Commander is great when I'm looking to play something outside of limited formats.
It's nice to play a format of MTG that doesn't require buying a whole bunch of new cards, lets me use my old stuff, and works well for multiplayer. And also tends to attract players looking more for an interesting game than just a quick win. Commander is great when I'm looking to play something outside of limited formats.