"Player: OK, I'm going to use my side deck now. I'll take out well, umm, three cards . . . maybe five . . . do I have to show you the cards? Can I take out just two and add four?

Opponent: Dude, we haven't started dueling yet. The match starts in a couple of minutes. Just chill . . ."

You get some weird questions about side decks at tournaments. At Regional tournaments, almost everybody has a side deck, yet I don't think most people are comfortable with what it is and how to use it. Used correctly, it can provide you with an awesome advantage against an opponent. That's one of the "secrets" of top duelists in the metagame—build the side deck so that you can neutralize the decks and strategies found in any specific local environment.

In fairness, some top duelists have a side deck and know exactly how to use it, but might go an entire tournament without ever needing it. Other duelists use it almost every match. The goal of this article is to make sure you know the mechanics of the side deck and, more importantly, how you can use it. Then you can decide with confidence at a tournament if and when you will use cards from your side deck.


The Basic Mechanics

The side deck must contain exactly fifteen cards—no more, no less. Other than that, the only real restriction on its contents is that the combination of your main deck and side deck must not violate the restrictions of the Limited and Semi-Limited Lists and must not have more than three of any one card that is not limited or semi-limited.

During a duel, your side deck is off the field and out of play. You cannot use or even look at your side deck during a duel.

You cannot use your side deck before the first duel of a match. After the first duel, you can exchange cards between your main deck and side deck before the next duel begins. You can exchange cards between the first and second duels, as well as between the second and third duels.

The ruling on side deck sleeves at the time of the writing of this article is that they do not need to be the same color as your main deck sleeves until you move the side deck cards into your main deck. The current rules are under review, but I strongly recommend that you use the same sleeve color. This will make the swapping process much easier. You just need to keep the side deck separate from the main deck to avoid confusion. A second deck box works nicely.

You can exchange as many cards as you want, from one card up to fifteen cards. However, for each side deck card you add, you must move one main deck card and place it with the rest of your side deck. After you trade cards between your main deck and side deck, your side deck must contain fifteen cards exactly; your main deck must have the same number of cards with which you started.

You do not have to show your opponent the cards you put in or took out. You do show your opponent the number of cards removed and put in, and your opponent can confirm that your side deck count is correct.

You must reset your main and side decks before each match begins. That means they must contain the same cards as when you started the first duel of the first match. This is really, really important, since the Penalty Guidelines state that you will receive a game loss if you have failed to reset your deck at the beginning of a match.

That's it for the rules and mechanics of the side deck—now on to how to build and use it.


Side Deck Strategy

There really are no "standard" side deck cards. What you should include in your side deck depends on your deck type. I counted more than 100 unique cards found in the side decks for the Top 8 duelists of nine different Regional tournaments from across the country. There is no such thing as a "cookie cutter" side deck.

The three main side deck strategies that I'm aware of are Counter, Slide, and Switch. You can also blend the strategies to create a hybrid side deck.



Counter

A Counter side deck is built to respond to, or counter, an opponent's deck as well as specific cards in an opponent's deck. For example, Kycoo the Ghost Destroyer is a great counter card for Zombie, Chaos, and Dark Necrofear decks, since Kycoo prevents the opponent from removing cards in either graveyard from play. When Kycoo is active on the field, your opponent cannot activate Book of Life, summon Chaos monsters, or summon Dark Necrofear—good card.

A typical example of this type of side deck and some of the deck types (not an exhaustive listing!) that the cards are used to counter is as follows:



Counter Side Deck
2 Kycoo the Ghost Destroyer (Zombie, Chaos, Dark Necrofear)
1 Torrential Tribute (Magical Scientist, Control)
1 Nobleman of Crossout (Exodia, Burn)
1 Poison of the Old Man (Magical Scientist, Burn)
1 Zombyra the Dark (Zombie, Beatdown)
1 Soul Release (Dark Necrofear, Chaos, Zombie)
1 Scapegoat (Beatdown, Change of Control)
2 Magic Drain (Hand Disruption)
1 Ceasefire (Exodia, Burn)
1 Spear Dragon (All defensive decks)
1 Book of Moon (Beatdown and Hand Disruption)
2 Electric Snake (Hand Disruption)

Of course, the quantities and specific cards will depend on your main deck, your local game environment, and the cards you prefer to play. For example, some players prefer Skill Drain and Dark Ruler Ha Des to counter specific deck types. Others would rather use a different counter trap than Magic Drain, such as Solemn Judgment.

However, you should not dream up scenarios and try to cram the side deck with obscure cards. Remember, you have to remove a main deck card to make room for each card from your side deck.


Slide
A Slide side deck is built on the principle that your main deck has a hybrid theme and that you can make it more or less of one theme through side decking. A good example is the following deck:

Sliding Beatdown/Control
40 cards total

Monsters
1 Jinzo
1 Vampire Lord
2 Mystic Tomato
1 Don Zaloog
2 D. D. Warrior Lady
1 Magical Scientist
1 Yata-Garasu
1 Exiled Force
1 Tribe-Infecting Virus
1 Fiber Jar
1 Witch of the Black Forest
1 Sangan
1 Sinister Serpent
1 Breaker the Magical Warrior

Spells
1 Dark Hole
1 Raigeki
1 Painful Choice
1 Harpie’s Feather Duster
1 Heavy Storm
3 Mystical Space Typhoon
1 Change of Heart
1 Snatch Steal
1 Mirage of Nightmare
1 Graceful Charity
1 Pot of Greed
1 The Forceful Sentry
1 Delinquent Duo
1 Monster Reborn
1 Premature Burial
1 Scapegoat

Traps
1 Imperial Order
1 Call of the Haunted
1 Ring of Destruction
1 Waboku
1 Torrential Tribute
1 Mirror Force

Side Deck
3 Drop Off
2 Time Seal
2 Torrential Tribute
1 Don Zaloog
1 Spirit Reaper
1 Confiscation
1 Nobleman of Crossout
1 Kycoo the Ghost Destroyer
1 Slate Warrior
1 Goblin Attack Force   
1 Gemini Elf


Notice that the deck starts as a Best-of-Breed Beatdown with some Hand Disruption/Control. The side deck allows the player to shift or slide the deck to a completely control-focused deck by adding Drop Off, Time Seal, Confiscation, Spirit Reaper, and another Don Zaloog. If the situation requires, the deck can slide the other way to become more of a Beatdown deck by adding Slate Warrior, Gemini Elf, and Goblin Attack Force.

The same concept can be applied to most deck types including Burn-Beatdown Hybrids, Deck Destruction–Stall, and special win condition decks.