The Side Deck

The side deck is the most important part of the game because it allows for a large amount of skill expression. This is mainly because it most of the games you play, will be played after both players have sided. This makes it crucial to understand what it is, and how to use it correctly.

What is It?

To discuss the side deck and its importance, we need to understand what it is. So, what is the side deck? The side deck is a collection of 15 cards, all of which are tech options for different matchups. However, it is inaccessible during actual games. During a match, you play a best of three against your opponent, and between the games you utilize the side deck.

These 15 cards you put in your side deck are very important because you are allowed to put them into your main deck, or extra deck, as long as you remove the same amount of cards you put in. So, if you add 9 cards from your side deck to your main deck, side in, you have to remove 9 cards from your main deck and move them to the side deck, side out.

Purpose

This can seem very niche at first, and difficult to use. However, the side deck is designed to serve one purpose, fixing your matchups. So, when building it, you want to add cards that beat the current meta. This will change depending on the event you go to, because the meta at your locals can be different from the meta at a larger tournament. Furthermore, you want to add cards designed to help you go first: Solemn Judgment, The Black Goat Laughs, etc. In addition to this you want cards that can help you go second: Mulcharmy Purulia, Lightning Storm, etc.

Then, between games in a match, typically a best of three, you will side cards in and out depending on the matchup and on whether or not you think you’re going first or second. If you won a game, it is usually safe to assume you’re going second, so you side in your going second cards. If you lost a game, you get to pick if you go first or second, so you side for what you think is best.

Artifact Lancea

In 2025, there was a period of time where most side decks included at least 3 copies of the same card. The card in question is Artifact Lancea. Lancea was used because one of the two best decks at the time, Maliss @Ignister, was a very banish heavy combo deck. Maliss was also able to play through most hand traps, and draw 3 cards while doing so. The deck is so good, that after being hit on the banlist throughout all of 2025, and receiving hits in 2026, it is still a top 5 deck (as of writing this). However, it was never the best deck because people found the silver bullet really quickly. The silver bullet was none other than Lancea. Lancea was able to win games by itself, or help another card do the job.

Smoke Screening

Sometimes, a player will choose to side neither going first, nor going second cards. Instead, they will choose to side a whole different deck. This practice is called “smoke screening”. Smoke screening is usually done with very small engines, or with decks than can afford to play part of the first engine in the main deck. An example of this could be playing Labrynth while siding Tenpai. Smoke screening attempts to catch the opponent off-guard with a weird side deck, to potentially get an easy win. However, this is not good nor worth doing. Smoke screening is a bad idea because the 15 slots in your side deck are the most important slots in the game. So, you would rather play cards that do something consistently, rather than cards that catch the opponent off-guard.

Debate

Recently, there has been some controversy surrounding the side deck. There have been some people who have wanted it removed from the game because it has been making games less interactive. In more recent formats, people have been siding cards that instantly win them the game: Dimensional Fissure, Mistaken Arrest, Retaliating “C”, etc. This has led to games after siding to be a lot more one sided. They also argue that the side deck makes games more about which decks have more silver bullets than others. An example of this could be Maliss @Ignister during ALIN format. It was arguably better than Mitsurugi Ryzeal, but it was held back by the fact that it had an obvious silver bullet: Artifact Lancea.

However, some may argue that the side deck is a necessary part of the modern game. They say that it allows people to prepare for matchups that the might otherwise lose. For example: a weaker deck could side cards that beat stronger decks to even the playing field. They also say that the side deck allows for a lot of skill expression, by making people think more when deckbuilding. Furthermore, they use Master Duel as an example of why a side deck is needed. Master Duel often allows for more explosive, and less consistent decks to be better because they don’t have to worry about the side deck.

Things to remember

When you’re building your side deck that are some things that are important to remember:

• Don’t side extra deck cards
  • Most decks are able to run all the extra deck monsters they need, and still have extra room leftover. This means that you have room to play the tech option in the extra deck.
• Think while building
  • While building the side deck, every slot counts. So, before putting in 9 cards against the best deck in the format, consider how good your matchup is. Then, you want to consider how much you expect to see the deck. Furthermore, you should consider how scared you are of the deck. Then, taking all of those factors into account, you can side an appropriate number of cards.
• Think about siding patterns
  • When you’re building the side deck, it is mostly theoretical. However, you have to keep in mind that the side deck will be used. So, while building make sure to play as many going first cards, as you’re playing going second cards in the main deck. This applies the other way as well.