Combo gets a bit of a bad rap in Commander. In newer playgroups it can seem like a cheap win; it comes out of nowhere and most decks are equiped to stop combat damage, not combos. This can seem like a bit of an unfair assessment. There are a lot of things that go into building a good combo deck and you often don't see all the effort that goes into building a combo deck from just one game.
Think of this as a simple guide to combos. These are the things that deck-builders need to consider when making a combo deck. This applies for both casual and competitive commander decks, but casual often won't have all of these factors, while cEDH combo will.
Synergy with commanderIf you can somehow incorporate your commander into a combo, do it. That's one less combo piece that you need to search up. For example,
Zaxara, the Exemplary easily makes infinite mana with
Freed from the Real. Then you just need an outlet for all that mana.
Najeela, the Blade-Blossom combos with
Druids' Repository (and a number of other cards).
Siona, Captain of the Pyleas combos with
Shielded by Faith. Keep in mind that including your commander as part of the combo is supposed to make things easier for you. If you're trying to make a 4 card combo work with your commander, it's probably not worth it. You also have to be careful about making your commander a target for removal.
Dead cardsOr rather, the lack of dead cards. A dead card is a card that is only good in the combo and is absolutely useless outside of the combo. Take for instance,
Deadeye Navigator and
Dockside Extortionist. These two creatures make infinite treasure tokens.
With this example,
Deadeye Navigator is the dead card. 6 mana and then some isn't really worth it outside of a combo.
Dockside Extortionist however is still useful, because he can also be mana ramp outside of the combo. When building a combo deck, you want to use the least amount of dead cards possible, so that way you don't get stuck with a lot of cards in hand that are otherwise useless.
LayeringThis part only applies if you plan on using more than one combo in the deck. Layering is when a lot of the same cards are used in two different combos. For example ,
Food Chain combos will often use
Demonic Consultation and
Tainted Pact to get
Food Chain, because it also might
exile Eternal Scourge or
Squee, the Immortal along the way.
Thassa's Oracle also benefits from these cards, as they can
exile the entire library for a win. Because these two combos use two of the same cards, they will often go together in deck building.
Infinite mana outletThere are a lot of combos that make infinite mana. Just remember that infinite mana on it's own does not win the game; you still need something to spend that infinite mana on.
Walking Ballista is a simple one.
Thrasios, Triton Hero is another one that gets used in the 99, paired with
Thassa's Oracle. The reasons why deck-builders use these cards is because they are not entirely dead cards;
Walking Ballista can still be removal and Thrasios can still be card advantage.
The best infinite mana outlet to use is your commander. Commanders like
Ezuri, Renegade Leader,
Kenrith, the Returned King, and
Oona, Queen of the Fae are used is because they can win the game with infinite mana. This is just another way that you can incorporate your commander into the combo.
Card advantageThis includes both card draw and search effects. Search effects get you into a specific card (your combo piece) while card draw gets you lots of cards. For a combo deck, you need both. I don't think I need to go into much detail about these two things, but I will say that combo decks need more search effects than say, a combat-based deck. If you're trying to assemble
Isochron Scepter and
Dramatic Reversal, there are no substitutes for either of those cards. You need to search for them.
ProtectionThis is the thing that more casual decks tend to
forget about. Experienced players are going to try to stop your combo with counterspells/removal spells. You need to protect your combo pieces. Above all you want your protection to be low-cost, because during combo turn you often won't have a lot of mana to spare. Some good choices are
Silence,
Pact of Negation,
Malakir Rebirth,
Deflecting Swat, and
Veil of Summer.
If you have any questions or comments, or if you think there is something I'm forgetting, feel free to reply to this thread.