My side decks I use to change th dynamic of My deck when I know a opponent has figured it out.Like I have seen before so many times a switch from a stall deck .next round they know what your upto but a quick shift of cards and a burn deck is born.
The side deck has useful aplication in the "mental game" many duelists also use.I have a original deck I use that a combo burn/suicide deck but in my side deck I have two final countdown and all I need to push the round forward so they finish there work.I for one know the look when a final countdown gets pulled first or second turn in a round.Just how badly they will push to destroy your life points.A simple advantage forcing your opponent to follow a stratagy you lay down instead of Him/Her following there own game plans.
Also I have a deck or two I have master using "delta attacker"I take alot of skill to keep three of the same type common monsters out on the field.So I keep in the side deck what I need to alter the deck to obtain what I want.dificult in some circles but oh so satifying.

The side-deck/board is different for everyone, as most can see by reading this article and posting thread. While there is the multi-purpose side-deck that anyone can use, most tend to create their side-deck based on their own deck. I find that the side-deck that works/complies with what deck YOU'RE running works better overall.

For my FIEND Side-deck I run:

Soul Demolition
Soul Demolition
Fiend Comedian
Fiend Comedian
Ceasefire
D.D. Dynamite
D.D. Dynamite
D.D. Dynamite
Mask of Darkness
Soul Release
Soul Release
Soul Release
Dark Necrofear
Return from a Different Dimension
Return from a Different Dimension

My side-deck is used to counter almost every deck possible that I encounter. Once Dark Ruler Ha Des is in the GY, and two other powerful fiends (Dark Jeroid), RFP for Dark Necrofear, and then RfaDD them back.

if I do ever make a side deck, I would make it for my sphinx/beatdown deck cause it only has 40 cards.

Its taken me so long to actually figure out how to make a side deck decently (or at least that's what i call it) that with whatever deck i use, usually my side deck looks like this, but most of the cards in it get swapped with my normal cards so often that the total 55 cards between deck and side deck are simply one. (i havent seen the forbidden list lately cuz the site is being weird so if there are any forbidden in this, tell me) this is what i got:
1. Heavy Storm
2. Tribe Infecting Virus
3 - 4. Giant Trunade
5 - 6. Night Assaillant
7. Forced Requisition
8. Raigeki Break
9. Tribute to the Doomed
10 - 11. Magician of Faith
12. Pot of Greed (usually is in my deck, but whenever i make a deck i put this in my side deck initially until i decide what i want to take out of my main)
13. Snatch Steal
14. Creature Swap
15. Magic Jammer

heres 2 side deck cards that virtually any deck can use:
prohibition
array of revealing light

prohibition stops one card, plain and simple. if they rely on one card to win lock down that card, even if they kill it it bought u precious time for more counters.

array of revealing light slows down theme decks, warrior, dragon, fiend, beast, etc. Also if they run a field card its murder, if u play gk decks use it after they play necrovalley and call spellcaster, watch them cry as they lose necro even if magic reflector was used, and all their monster have to wait to attack.

I agreed

My side deck is Tech Expansion of my deck

Mobius the Frost Monarch
Mobius the Frost Monarch
Apprentice Magician
Apprentice Magician
Nobleman of Crossout
Nobleman of Crossout
Smashing Ground
Smashing Ground
Time Seal
Time Seal
Giant Trunade
Giant Trunade
Kycoo the Ghost Destroyer
Magic Cylinder
Delinquent Duo

My Final Countdown Side:
Lava Golem x2
Wave Motion Cannon x2
Crimson Ninja x2
Royal Oppression x2
Mask of Restrict x2
Soul Release
Messenger of Peace
Barrel behind the Door
Pikeru's Circle of Enchantment
Hallowed Life Barrier

It sides into a Lava Burn. It also has some anti Burn cards incase the other player Sides into burn.

Royal Oppression is a great Tech Card

Crimson Ninja's are there for Royal Decree's and they can be Meta'ed into TER's.

Soul release is a great Tech card and should be used more.

Masks of Restricts are the Anti Mobius/Tribute off Lava Golem.
The rest is self-Explanatory.

My Phoenix is farily Generic when it comes to its side. That way I only have to make Minor Modifications if I want to use it in another offensive deck:

Dust Tornado x2
Kinetic Soldier
Drop off x2
Soul Release
Solemn Judgment
Cursed Seal of the Forbidden Spell x2
Divine Wrath
Barrel behind the Door
Hallowed Life Barrier
Pikeru's Circle of Enchantment
Mobius the Frost Monarch x2

Some Anti Stall, Tech cards like Drop Off. Cursed Seals for those OTK decks (The Deck out ones) and the Decks that use field cards, or one Spell Card in particular (Final Countdowns)

I understand the concept that some people relay of, "I build my deck to be effective against about any kind of deck." Sorry, I'm not buying it. If your deck has cards to counter almost every kind of deck then it's likely your deck has no real focus and while it does a little of everything it likely doesn't do anything extremely well.

Now, before I get a boat load of posts agaist what I've said above I need to add that's the probability. I'm sure that someone out there has an effect deck against most convential deck types. I'm sure you've noticed though the expanding number of deck types that are seen at major tournaments. You can't counter them all effectively with one deck, not that I've seen anyway, not without a well built side deck that addresses the one or two major weaknesses of your deck.

I've seen as much high level play as anyone else out there, I can gurantee you that you won't see any one of the players this year who make it to the world championships without a side deck that they go to often and are so thankful that they have it available to them.

One of the most consistant factores I saw in last year's top 8 at nationals was their excellent side decking capabilities. I'm certain it made the difference in a couple of matches in the top 8 between advancing and packing it in for that year.

When you post a deck online for review, include your side deck. Let others help you with your selections. It's not even enough to have a good side deck, you should know exactly what you'd take out of your main deck and replace it with against any given deck type you're up against. Remember, you only have 3 minutes to side deck. Don't take up your side decking time with changing sleeves. Put your side deck in the same sleeves your main deck has.

As a suggestion, make a copy of your deck list or at least jot down your side deck list and keep it in your deck box. In this way you'll easily be able to de-side deck quickly. Often times there isn't but 3-7 minutes from the ending time of the round you're in until the beginning of the next round. You don't want to be scratching your head trying to remember just what your side deck is suppose to be comprised of. Failure to de-side deck is a game loss should you be deck checked. While that may seem silly to some that someone could make that mistake, I know that at most regional tournaments I'm I judge, on an average one every other regional tournament of the top eight players ends up with a game loss for failure to de-side deck.

Take advantage of the extra possibilities folks. That's 15 extra possibilities you have access to. Don't waste them.

My current sidedeck:

{1} Jinzo
{1} TIV
{1} Agent of Creation - Venus
{1} Cannon Soldier (for all those duels when first damage wins)
{2} Spirit Reaper
{1} MoF
{1} Metamorphosis
{1} Level Limit Area B
{2} The Dark Door (can anyone say Anti-Warrior?!!?)
{1} Magic Cylinder
{2} Interdimensional Matter Transporter
{1} Ceasefire


It may look a little strange compared to others (yep TIV is in there, along with Jinzo), but then my current deck's just as odd. I doubt anyone could guess at it.

And no deck can be built to handle absolutely everything - there will always be one weakness that your opponent can exploit.

Here's the Side Deck for my Deck. It actually comes in handy when the occasion rises

Horus The Black Flame Dragon Lv 6 (X2)
Horus the Black Flame Dragon Lv 8 (I love this guy!!!!)
Phoenix God of Nephthys (I like to break him out on occasion)
Anti-Spell Fragrance (Fun to mess people up with)
Pikeru's Circle of Enchantment (Anti-Burn)
Barrel Behind the Door (Anti-Burn)
Big Burn (Anti-Exodia, Anti-Chaos, Anti-Zombie)
Graceful Charity (Extra Draw Power)
Soul Release (Anti-Exodia, Anti-Chaos)
Altar for Tribute (Anti-Burn. Great against Lava Golem)
Spell Absorbing Life (Anti-Flip Effects, Life Gain)
Exchange (Anti-Exodia)
Sonic Duck (X2) (1700 ATK 3 Star)

I know what everone's gonna say "Why is Graceful Charity in your SIDE DECK???" Answer: With the way my deck is built I cannot afford to discard 2 cards to the graveyard like that. I have enough discardsing as is.

Normally what I do is just side in and out the Horus Dragons for my other Trubute Monsters, Mobius, Phoenix and Silent Swordsman Lv 5. If I run into one of the troublesome decks like burn or Exodia I'll side in my weapons against it.

I also have been known to make side decks that make my deck two decks in one. I'm at work collecting Silent Swordsmen so that I can make a side deck for my Mystic Swordsman Deck to make that two decks in one.

i think when building a side deck you should try and look at the most populare themes

warrior
chaos
burn
pheonix
and
vombie

luckly most people will mix these decks so it easy for you to stop them.

for warrior and chaos one of the best cards you can use is kinetic soldier or bottomless trap hole.

mobius and swarm of locusts/scarabs is good against burn

and just bottomless trap holes and compulsurys.

a side deck should contain most of those cards plus added spell/trap removal such as dust tornados and mataza the zappas or another little level 3 to stop burn.

i give up on sidedecks as i always lose them and find them after tournys :P

hope it helps

whote mage

My side deck is a reflection of the strange metagame that my area has. Gravekeeper, Burn, and tribal decks run rampant. My side deck is mostly to combat the swarming of the Gravekeepers and the lock down of the Burn decks:

1. Mobius the Frost Monarch
2. Zombrya the Dark
3. Zombrya the Dark
4. Zombrya the Dark
5. Exiled Force
6. Nobleman of Crossout
7. Nobleman of Crossout
8. Array of Revealing Light
9. Array of Revealing Light
10. Solemn Judgment
11. Solemn Judgment
12. Deck Devastation Virus
13. Ceasefire
14. Dust Tornado
15. Dust Tornado

As you can see, lots of added Spell/Trap removal, with a few beatsticks thrown in to help take out the Gravekeepers.

You'll never catch me with a side deck! I think they're pointless.

Against Burn Decks: Blowback Dragon, Mobius the Frost Monarch, D.D. Crazy Beast, Mataza the Zapper, Mystic Swordsman LV2, Giant Trunade, Barrel Behind the Door, Hysteric Fairy, Dust Tornado.

Dark Jeroid and D.D. Assailant works against Phoenix. TIV here is not in your Deck.

An average side deck of mine will look like this.

2x Mobius the frost Monarch
2x King tiger Wanghu
1x Mystic Swordsman LVL 2
1x Spirit Reaper
1x Swarm of Locusts
1x Magician of Faith
1x Apprentice Magician
1x Metamorphosis
1x Giant Trunade
1x Ceasefire
2x Dust Tornado
1x Sakuretsu Armour