If you were a fan of the Yu-Gi-Oh anime or the older booster packs, there's a good chance that you've heard of Gate Guardian. The original version was insanely difficult to summon; requiring you to tribute Kazejin, Suijin, and Sanga of the Thunder on your field in order to summon it. Heck, Sanga, Suijin, and Kazejin themselves required 2 tributes in order to get them onto your field. You'd need a total of 6 monsters just to get them out.
Thankfully, there's a brand new iteration of this big boy in the form of a whole new archetype!
The new Gate Guardian archetype is wildly underrated. While the current meta in Master Duel is filled with Yubel, Snake-Eyes+Fire King, and Branded+Despia decks, Gate Guardian is able to counter a lot of their best plays and shut them down.
You will still need Sanga, Kazejin, and Suijin, but you do not need to worry about tribute summoning them. There's loads of support available to help you get those 3 out on the field and get your boss monsters out. In fact, you don't even need to have them on the field for the best monster in the deck. From now on, I'll refer to Sanga of the Thunder, Kazejin, and Suijin as "The Big 3" to save some time.
Boss Monsters
Rathan than relying on just one Gate Guardian, you now have 4 different versions, each with a different effect. Each one is a fusion monster that can be summoned by banishing the required material from your field. In the case of GG Combined, they can be banished from your hand, field, or graveyard.
Gate Guardian of Thunder and Wind: Used for searching your deck for a spell or trap that mentions the big 3 (Sanga, Suijin, and Kazejin).
Gate Guardian of Wind and Water: Has a spell/trap card negate that you can use twice per turn.
Gate Guardian of Water and Thunder: Can reduce an opponent's monster's attack to 0.
Gate Guardians Combined: The biggest boy. Has an effect that negates monster effects that target your card(s) and can be used thrice per turn.
On top of having some already stellar effects, the Gate Guardians come with very handy floating effects (effects that activate when they're destroyed, banished, etc.) to keep them in the game and help you recuperate your losses. The best part is that they work almost no matter what. They'll trigger as soon your monster leaves the field; meaning that it will trigger from being destroyed in battle, by card effect (monster, spell, or trap), banishment, returning to the extra deck or hand, being sent to the graveyard, or even being used as a tribute.
The first 3 fusion monsters allow you to summon one of the monsters used for their fusion summon as long as they're banished. So no matter what, you'll get a Sanga, Kazejin, or Suijin back on your field. But Gate Guardians Combined allows you to summon a different Gate Guardian monster from your deck or extra deck; meaning that you could summon any of the Gate Guardian fusion monsters, or even Dark Guardian (he is treated as a Gate Guardian while in the hand, deck, or graveyard).
Having GG of Wind and Thunder on your field alone is enough to shut down an opponent's turn. But combing them with other GG fusion monsters or generic support is never a bad idea.
Dedicated Support Cards
Any archetype can have amazing boss monsters, but it's the support and smaller monsters that make a huge difference. Luckily, Gate Guardian has loads of support. We'll start with the monsters.
Shadow Ghoul of the Labyrinth: Discard him from your hand to get the field spell from your deck to your hand. You can also banish him from your graveyard to automatically destroy an opponent's monster that battles any one of your monsters during the battle phase.
Labyrinth Heavy Tank: When summoned, allows you to get one of The Big 3 out of your deck and onto your field as a continuous spell. If the field spell is on the field when you use this effect, you can destroy one of your opponent's monsters.
Dark Guardian: Can be summoned either by the effect of "Dark Element" or by shuffling The Big 3 from your hand, field, graveyard, or banishment into your deck. If summoned using Dark Element, it is unaffected by your opponent's monster and spell effects.
Now let's get to the spells and traps.
Labyrinth Wall Shadow: Not only does it help search for one of The Big 3, but it also stops monsters level 4 and below from attacking on their turn they're summoned and destroys a monster with 1600 attack or less during the battle phase.
Riryoku Guardian: If your life points are lower than your opponent's, your opponent's life points are cut in half and that amount is added to the attack of one of your Gate Guardian monsters.
Double Attack! Wind and Thunder: Can destroy 1 card on the field.
Dark Element: If you have a GG monster in your graveyard, you can pay half your LP to summon another GG from your hand, deck, or extra deck.
Prey of the Jirai Gumo: A trap monster (trap card that can be summoned as a monster when activated) that destroys an opponent's monster in the same column as this card.
The spells and traps also have awesome floating effects that let you add to your hand one of The Big 3 from your deck or that is banished. Great for helping you get those pieces out of your deck and into your hand, speeding-up the whole process of summoning GG Combined.
Dark Guardian is nearly unkillable and basically acts as an extra beatstick. You could even use him as material for link summoning. Wall Shadow and Heavy Tank are mostly meant for searching out The Big 3.
Generic Support
Remember how I said that the GG spells and traps have those floating effects? Whip out a Heavy Storm! Set those spells and traps and let it rip, baby. While you may not get the benefit of their first effects, the floating effects are just as good, letting you add one of The Big 3 to your hand at the cost of banishing the spells or traps from your graveyard. You could even use Card Destruction to send your whole hand to the GY, draw a new hand, and BAM - you've not only dumped the spells and trap into your GY, but you've also dumped The Big 3 into the GY and you're all setup for GG Combined.
Another great combo is the Magicians' Souls + Illusion of Chaos engine.
Activate Preparation of Rites to add Illusion of Chaos from your deck to your hand.
By revealing Illusion in your hand, you can add Souls from your deck to your hand.
Using Souls' effect, send Kazejin or Illusion from the deck to the GY, summon Souls to the field.
Activate Souls' effect to send up to two spell/trap card(s) from your hand or field to the GY and draw that many cards.
Using either method to get the spells and trap into the GY and using their ability to search for the Big 3 greatly helps with getting GG Combined onto the field.
Super Polymerization is a must-have in this deck. Or any deck, for that matter. Part of Super Poly's effect makes it so that cards and effects cannot be activated in response to Super Poly's activation. This is excellent for disrupting your opponent's plans - either during your turn or theirs. It's especially helpful against Yubel and Fire Kings, who both benefit from their monsters being destroyed. With the effect of Super Poly, they're instead just being sent to the graveyard.
Skill Drain can be used in this deck to really screw your opponent. Sure, you'll lose your negates. But any plans that your opponent had are ultimately trashed. Not to mention that GG Combined and Dark Guardian all have very high attack power and can aggro your opponent to death without their effects.
That leads us to the generic extra deck options. Garura, Wings of Resonant Life is your go-to for when you slap your opponent with the Super Poly. On top of that, you can draw a card when it's sent to GY.
Another great one to have is S:P Little Knight. This allows you to counter an opponent's card effect or activation by banishing your opponent's monster and one of your monsters until the end of the turn. If you used another extra deck monster as material for the link summon of S:P Little Knight, you can even banish a card on the field as soon as it's summoned. You could potentially use Magicians' Souls as material to link summon Relinquished Anima and then link summon Little Knight. You could even use Garura and another monster, and draw a card due to Garura's effect.
These are just what I prefer to use though. If you decide to make a deck of your own, you can use whatever combos you like. Honestly, there are so many good ones that work with this deck.
Final Thoughts
I've gotten so far into the latest Duelist Cup with this deck. If you'd like to test out the deck that I used (which I found on Reddit), click right here and check out that decklist. I've used that as a base for my deck and tweaked it as I went along.
Gate Guardians enjoy so many negates and floating effects that it's hard to NOT have a GG on the field at all times. Quite honestly, their greatest weakness is that they aren't the best when going first. The most that you can get out on turn 1 (if you don't get slammed by handtraps) is GG Combined and S:P Little Knight. Gate Guardian has very little swarm in the early game, and as a result aren't able to take advantage of other generic support, like Baronne de Fleur or Apollousa.
If you do end up going first and you get trounced by your opponent in some way, you can still pivot off of that pretty easily and swing the duel in your favor - depending on the opponent.
Pros
Easy to use, once you get the hang of it.
Plenty of effects that can negate and cripple your opponent that can be used multiple times per turn.
Very versatile, can be used with many other engines and archetypes.
High attack.
Cons
Very little swarming in early game.
Very susceptible to Nibiru or Kaijus.