Rules

Kingdom Duels aims to provide a similar experience to the Duelist Kingdom arc of the anime. It follows the regular Yu-Gi-Oh! rules but with some differences. Players can agree to modify the rules (or even the cards) as much as they want (just like the writers did in the show!) Have fun!

📄 Getting Started

🗺️ The Game Board

The board has a Frontrow (five card zones where you play monsters), a Backrow (five card zones where you play spell and traps), a Rule Zone (where you play rule cards), your Main Deck Zone, Extra Deck Zone and Graveyard.

🧭 Setup

Each player begins the Duel with 2000 Life Points (LP).
Each player needs a Main Deck with exactly 30 cards and an Extra Deck with up to 20 cards.
Before the duel starts a Setup Phase occurs:
- Each player place their shuffled Main Deck and Extra Deck in their corresponding zones.
- Each player is allowed to activate Setup Rule card(s) that they may have in their Extra Deck.
- The starting Terrains are placed in each side of the field.
  - If a player didn’t play a Field Setup card, they must use 5 “Land” Terrains.
- Players then decide who goes first (by coin toss, rock-paper-scissors, etc.)
- They draw their initial 5 cards.
- If a player played a “Duelist Setup” Rule card, they may swap up to 2 cards from their starting hand with card(s) in the “Cardlist” of that Duelist Setup.
- The duel begins.

⚙️ Turn Structure

Draw Phase → Standby Phase → Main Phase 1 → Battle Phase → Main Phase 2 → End Phase

✋ Draw Clarifications

During its Draw Phase, a player draws 1 card from their deck (even in the first turn).
There is no hand size limit.
If you add cards from (or to) your Deck you must shuffle it afterwards unless otherwise stated.
If a player can’t draw cards from its Deck then that player loses the duel by deckout.

📌 Main Phase Clarifications

During your turn you can perform one Normal Summon and unlimited Special Summons.
You can Normal Summon in face-up ATK or face-up DEF Position Main Deck Normal monsters of any Level without tributing.
You can’t Set monsters in this game. Instead you can Hide a monster (or Summon in Hidden position) in face-down ATK or face-down DEF position but only if there is an effect that allows you to do so. Monsters with the FLIP keyword can be summoned in Hidden DEF position in any terrain that they can be summoned on.
Monsters Hidden in DEF Position work exactly like face-down DEF position in the official rules. Monsters Hidden in ATK Position are revealed during combat, but can be hidden once again after battle calculations if they are still on the field.

⚔️ Battle Clarifications

You can’t attack your opponent’s LP directly.
Only one monster can declare an attack on each Battle Phase.
Attacks can be redirected. If an attack is redirected then it is now treated as an opponent attack, even during your own Battle Phase, but its source is still considered to be the original monster.

⛰️ Terrain Markers

Example of a field with 5 Forest Terrains and two monsters Hidden (face-down), one in ATK and one in DEF.

On top of each Monster Zone in the Frontrow there will be a “Terrain Marker” (also called Terrains) that may give different effects to the monster card placed on top of it. They are components that recreate the diverse terrain effects of the anime, are not considered cards and are associated to the Monster Zone directly beneath them.

If a Terrain Marker is replaced by a new one then the old one must be set aside of the board in no specified zone.

If a monster is somehow summoned in the backrow, it is considered to be in the same Terrain as the corresponding frontrow Monster Zone in the same column.

Field Setup Rule cards define the starting Terrains that will be placed on each side of the field. If you don’t play a Field Setup Rule card during the setup of the game you are playing on the default rules and you must fill your Frontrow with “Land” Terrains.

🏞️ Field Power Bonus

In this example: 'Beast', 'Insect' and 'Plant monster types gain the Field Power Bonus.

“Field Power Bonus” is a term that is used when a monster is receiving an additional ATK and DEF increase thanks to the Terrain it’s located on. The ATK/DEF gain through this effect corresponds to 30% of each monster’s original ATK/DEF and is printed on every card.

Each Terrain Marker states which type and/or attribute (if any) gains the Field Power Bonus and this is represented in a specific section between the Name and Effect box.

🎴 The Cards

🗒️ Components of a Card

Attribute Symbol: can be one of the six attributes (DARK, LIGHT, FIRE, WATER, EARTH, WIND) in the original game (minus DIVINE). All cards have an attribute including spell and traps.

Grade Symbol: The grade or “main icon” of a card provides specific information about how that card is played. It varies from card type and card subtype. These are Levels (numbers 1 to 12 on top of an orange and yellow star-pattern icon), Glyphs (icons for Normal, Equip, Continuous, Setup) and Charges (a numeric value on top of a dark purple icon used for Symbol Rule Cards)

Field Power Bonus: a numeric value with plus sign near the ATK/DEF that indicates how much ATK/DEF the monster gets when is receiving a field power bonus.

Effect Box Icons: a dark arrow icon (►) is used to split the condition to activate it and the actual effect. An empty square icon (□) is used to make a list of options.

Types: Is a categorization of words that a card may have. They don’t provide effects but are used as a reference for multiple cards and effects.

📜 Rule Cards

Rule Cards (light green frame) are placed in the Extra Deck and can only be played into the Rule Zone. If they leave the Rule Zone they go back to the Extra Deck.

Rule Cards have effects or mechanics that are added on to the current game ruleset for as long as that Rule Card is active on the Rule Zone. These effects cannot be negated and there is no limit to the amount of cards that can be played in your Rule Zone. They may have one of the following types: Normal, Setup (Game, Field, Duelist, Challenge), Symbol.

Normal Rule Cards (they simply say “Rule” in their Type) have two different ways they can be activated:

If they have a “KEYWORD:” condition, they can be activated from your Extra Deck into the Rule Zone whenever you have a face-up card in the field that has a Keyword (a Type or Attribute either in the card or mentioned in the card effect) that matches its activation condition (this is a Quick Effect unless otherwise stated).
If they have a “RELIANCE:” condition, it means that they can only be activated by the effect of specific card listed there. If the card that activated it leaves the field then this card also leaves the field (unless it specifies that the Reliance is on activation only).

Setup Rule Cards are a subset of Rule cards that can only be played during the Setup Phase before the start of a duel, and each have a different treatment depending on its type:

→ Game Setup Rule Cards are large changes that modify the entire game in a big way. They must be unanimously agreed by all duelist to be activated during the Setup Phase. Only one Game Setup Rule may be active at once between all players.
→ Field Setup Rule Cards are used to declare the 5 starting Terrain Markers you control. They are specified in a “Terrains” list, marking their positions from left to right in your side of the field. If both players agree they can play “Matched” Field Setup Rule cards, that have the same name but different setup (for example blue side and red side). You may only play one Field Setup per duel.
→ Duelist Setup Rule Cards are a representation of a Duelist from the anime you are playing as. Duelist Setup cards have a “Cardlist” which contains card(s) that can ignore the Restricted List during Deckbuilding. They also allow you to manipulate your hand during the Setup Phase. You may only play one Duelist Setup per duel. In the Setup Phase, after drawing their starting hand, a player may choose to replace up to 2 of those starting cards with any card listed in the Cardlist (the card must be revealed when being added to the hand, and a player can only add one individual copy of a different card this way).
→ Challenge Setup Rule Cards are completely optional and are a way to set some self-limits for yourself during deckbuilding by having to follow the specific restrictions that the card itself defines.

Symbol Rule Cards are represent objects or powers from the anime that can interfere in the duel (like the Millennium Items). They are optional to the duel, meaning that all players must unanimously agree if they want to play with them or not before the duel starts (they can also agree to let observers of the duel activate their symbol cards to influence the duel). You may only play one Symbol Rule Card per duel.

They work with a “charge” system which means that activating their effects (that are Quick Effects unless otherwise stated) consume a certain amount of charges that the card must have or they cannot be activated.
Symbol Effects have a flavor name for each effect which has no impact on the gameplay.
A player can only activate one of their Symbol effects per round.
Symbol Rule Cards must be played to the Rule Zone during your Main Phase first (as a Slow Effect unless otherwise stated), before being able to activate the effects.

🐉 Monster Cards

Normal Monster cards (yellow frame) are placed in the Main Deck (and have effects despite being called “normal” monsters, unlike the original yugioh).

Extra Deck Monsters (ritual, fusions, alters and integrations) have special summoning conditions that you must fulfill to play them from the Extra Deck onto the field.

Cards used for an Extra Deck summon are considered “Materials” of that card type (for example Fusion Materials or Ritual Materials).

🌀 Fusion Monster Cards

Fusion Monsters (purple frame) represent a combination of two or more specific monsters into one single being.

To summon a Fusion Monster you need to have a card named “Fusion” and the required monsters in your hand and/or field, and then attach the corresponding Fusion Materials to it. Fusion monsters are treated as having the same name as all their Fusion Materials for card effects.
If a Fusion Material somehow enters the field as a monster while its corresponding Fusion Monster is still on the field then this new monster can’t declare an attack on the first turn it’s summoned.

🕯️ Ritual Monster Cards

Ritual Monsters (blue frame) represent sealed monsters being summoned to the battlefield by sacrificing cards in a ritual ceremony.

To summon a Ritual Monster you need to fulfill the requirements of a specific Spell Card listed in its summoning conditions, and then send the corresponding Ritual Materials to the graveyard.
The spell card used to Ritual Summon usually remains on the field face-up until the ritual requirements are successfully fulfilled or the card is destroyed. The controller of that spell card can also send it to the Graveyard at will during its Main Phase. A monster equipped to another monster is still treated as a monster on the field and therefore can be used to fulfil a Ritual Summon. This is not the case with attached monsters (unless otherwise stated).

🔃 Alter Monster Cards

Alter Monsters (red frame) represent monsters that went through a transformation of some kind without merging with other monsters.

To summon an Alter Monster you need to play a card that lets you Alter Summon the specific Type while controlling a specific monster on the field listed in the conditions of the Alter Monster, and then attach the corresponding Alter Materials to it.
In some cases an Alter Summon may require a certain amount of “Summoning Counters” placed on top of the specific Alter Material as part of its summoning condition. These counters are usually placed due to card effects, and are removed once the Alter Summon is completed or the Material is removed from the field.
An Alter Monster is summoned on the same zone its corresponding Alter Material was, and any Equip card active on that monster is re-equipped to the new card instead (if the new target is still valid). Any attack or effect targeting the material monster now targets the new monster (if valid).

🧍 Integration Monster Cards

Integration Monsters (brown frame) represent cards that are combined with a duelist that represent you as a player.

To summon an Integration Monster you need to have had played a specific Duelist Setup Rule card at the beginning of the game (marked in the summon condition with curly brackets) and Erode from your hand or field the other Material(s) listed on the card.
If you want to summon in Hidden ATK or Hidden DEF an Integration Summon you are not forced to reveal the eroded material card at that moment, but when you erode it you must set it clearly apart from other cards, and once your monster is revealed or the duel ends you must reveal that it is the proper material, otherwise you lose the duel instead.

🔮 Spell and Trap Cards

Spell Cards (green frame) and Trap Cards (pink frame) are placed in the Main Deck. They have Attributes like Monster Cards, and may be one of the following types: Normal, Equip, Continuous. They are all Quick Effects except Equip Spells and Continuous Spells which are Slow Effects.

Spell Cards can be activated from the hand or from the field (if they were Set face down) while Trap Cards must be Set face down in the backrow first for a turn before being able to be activated.

Trap Cards have a “Trigger” condition which indicates that the card effect is automatically activated when that trigger is met (the player has no control over this activation). If the card says that the Trigger is “None” then you can activate the card at will (considering any other activation condition that the card may have).

If the player does not activate a trap card when its Trigger is met then the player gets an Idle Warning. If there are multiple of your traps on the field whose conditions are met at the same time: you can choose how many of them to activate (min. 1) without getting an Idle Warning.

Continuous Trap Cards with “Triggers” can be flipped face-up at any time their effect speed allows it, but the effect only activates when the Trigger is met.

Spell and Trap cards can have the auxiliary “Persist” type that indicates that the card remains a certain amount of time in the field after its activation (the condition is specified alongside the Persist type in each card).

🌈 Other Cards

There are a few Main Deck cards that have a combination of two colors in their frame. These cards are considered as having both their card types at the same time. They are Spell Monsters, Trap Monsters and Spell Traps. You can choose to play them as one card type or the other. Each card specifies how to play them with a “Play” condition on its text.

Token cards (gray frame) must be kept aside from the game and only brought up to the board when played by an effect. Tokens are considered Normal Monsters unless otherwise stated. Tokens can’t be attached to other cards and thus cannot be used for summoning methods that attach their materials. When Tokens leave the field they are removed from the game.

Emblem cards (light yellow frame) are non-playable cards that are just symbolic.

📿 Divine Cards

Divine is a special Type of cards that is usually found in monster cards but can also be found on other card types aswell. Each divine card is color-coded individually, meaning that it can have the frame color of its card type (main deck monster, fusion monster, spell, etc.) or a different color entirely. They have a special mechanic called “Hierarchy”.

Hierarchy is a scale that goes from 1 to 10. Divine cards of higher Hierarchy are unaffected by divine card effects of lower hierarchy. All non-Divine cards are treated as having a Hierarchy of 0. Hierarchy is represented on a card in the Type section as a single number with a different font, always as the last item in that section.

📃 Terminology

Effect Speed is defined as Slow Speed and Quick Speed (analog to Spell Speed 1 and 2 respectively, there is no Spell Speed 3). Quick Speed can respond to Slow or Quick effects, but Slow Speed can’t be used to respond to other effects.

Blue and Red: Every duel has two opposing sides: Blue and Red. Players must choose which color they belong to at the beginning of the duel in the Setup Phase. Some cards reference Blue/Red Side, in which case they refer to the side controlled by the player(s) of that color. This is applicable to multiplayer rules too.

Tilemap: Some cards can create a “Tilemap” which means that, using the artwork of that card as a reference, they create a grid of Tiles (squares) and Obstructions (black lines) for monsters and other cards to be played in. There can only be one Tilemap in the duel at a time. A monster must be on a specific Terrain to be inside the Tilemap. Monsters inside a Tilemap can only move and attack within Tiles of that Tilemap. If a monster inside a Tilemap were to move or be moved by a card effect to a different Terrain it now moves to a different Tile instead.

Tiles: Within a Tilemap, a Tile is a square in where a monster can be played in. A monster can only occupy one Tile at a time. A monster can move or be moved to another adjacent Tile horizontally or vertically (not in diagonal) if an effect allows it and the path between those tiles is not obstructed. A monster can only attack other monsters that are within one unobstructed Tile from it. A Tilemap can have Tiles of different colors with different effects, but unless otherwise stated all Tiles are White Tiles. Red Tiles and Blue Tiles (also known as Player-colored Tiles) are controlled by the respective player(s) of that color.
Obstructions: Within a Tilemap, an Obstruction is a line that separate one tile from another and prevents a monster to move through it or attack through it, unless otherwise stated. The outer limit of the Tilemap (the white space without tiles) is considered an obstruction that cannot be removed through any means.

Piercing Damage: If a monster attacks with an ATK that is higher than the DEF of a monster in DEF Position, the attacking player inflict the difference as Battle Damage.

Destruction Damage: If a monster is destroyed by a card effect that says “apply Destruction Damage”, then the controller of that monster receives damage equal to half of its ATK (this is called ‘Destruction Damage’ and is considered Effect Damage). You can’t inflict more than 1000 LP of destruction damage per turn.

Erode: If a card is eroded it means that it is completely removed from play to a non-specified area (its not considered to be on the field, deck, graveyard, hand or zone).

Permanently: If a card says to do something permanently it means that that action is done for the remainder of the duel, regardless if the card leaves the field or not.

Unstoppable: used in conjunction with Slow or Quick speed, if an effect is Unstoppable it means it cannot be responded by another card, and it cannot be negated.

Battle Swap: change the battle position of a monster.

Battle Lock: set the battle position of a monster for a number of turns (if no turn is specified then it’s permanent as long as this effect is active). Its controller cannot change its battle position normally.

📝 Effect Types

EQUIP: An equip effect is active when this card is equipping another target (usually placed in the backrow unless otherwise stated).

ATTACH: An attach effects is active as long as the card is attached to another card (which means that is placed beneath it in the same zone of the field).

DETACH: This effect is activated if you manually detach (send to the graveyard) this card while attached to another card (this is a Quick Effect unless otherwise stated).

FLIP: The effect is activated when this card is flipped face-up (either by battle, by an effect or by manually flipping the card face-up).

COIN: Toss a coin and call it. [O] means you were right on your call while [X] means you were wrong. The card itself specifies if the effect activates when you were right or wrong.

DICE: Roll a six-sided die, if the result matches what is between brackets you must activate that part of the effect. For example [1] means the result is exactly 1, or [2|3] means the result is either 2 or 3.

STRIKE: A monster in ATK Position with STRIKE is able to attack a Terrain Marker instead of a monster. The card may add a specific restriction to what kind of Terrain you can activate STRIKE on. You can only activate a STRIKE once per turn during your Main Phase 1 and you skip the Battle Phase that turn. This is still treated as an “attack” in game mechanics but it doesn’t actually battle or destroy any monster currently in the attacked terrain unless otherwise stated.

💤 Idleness Rule

During your End Phase, if all the following conditions are true then you get one “Idle Warning”:

Your opponent has at least 1 monster on their side of the field.
You didn’t had at least 1 monster on your side of the field this entire turn.
There wasn’t an effect preventing or negating your summons this turn.

If you already had an “Idle Warning” prior to this turn then you lose the Duel by game mechanics instead.

☕ Clarifications

Some syntax clarifications (portraying text of the cards within brackets):

{ only on a “Rulebook” monster } This means a monster that has the word Rulebook in its name.
{ only on “Rulebook” } This means a monster exactly called Rulebook.
{ only on a Rulebook monster } This would mean that Rulebook is a Monster Type.

Effects cannot miss their timing. Every “Once per Turn” is a hard once per turn. Every optional effect that needs to be activated by the player is also a hard once per turn. Every “Once per duel” is a hard once per duel.

To tribute a monster is to send it to the graveyard to fulfil a cost or effect, there are no Tribute Summons in this game.

Surrender Card is an informal term used for forfeiting. Placing your hand on top of the deck means you surrender the duel.

Cards can be face-down on the field when they are Set (spells and traps) or Hidden (monsters). When you flip a monster face-up you can flip it in either ATK or DEF position. If it’s flipped by your opponent it is flipped in the same position it was, unless otherwise stated.

During regular combat if the attacked monster changed somehow (it went into hiding, changed control, moved, fused, etc.) a replay occurs (meaning the attacking player must choose an attack target again after that first attack was declared).

If you take control of a card you must place it on your side of the field unless otherwise stated. If it was a monster you also take control of all the equipped cards to it but they remain on their current zones. To swap control refers that a specific player takes control of the card.

If a monster card states that it can move or be moved to another Terrain it always refer to an unoccupied Terrain from the controller of the card unless otherwise stated.

There are certain cards that can equip things other than monsters like “Equip the Deck” or “Equip the Graveyard”. In this case the equipping card remains on its zone and is considered to be equipping/targeting that game zone in its entirety.

Additional notes for Equipping and Attaching:

Equipped cards must be placed on the Backrow, while Attached cards must be placed beneath their targeted card.
To Equip a card you need an effect that allows you to do so or to have that card be of the Equip Type (Equip Spell or Equip Trap).
To Attach a card you need an effect that allows you to do so.
If a card leaves the field, all other cards equipped to it are destroyed (unless otherwise stated), and all cards attached to it are sent to the Graveyard (unless otherwise stated).

Additional notes for Hidden monsters:

Hidden monsters receive Field Power Bonus normally like face-up monsters.
You can’t equip or attach cards to a monster that is already Hidden. Cards that were already equipped or attached to a Hidden monster stay face-up on the field though.
Hiding a face-up monster is not considered a summon but a game mechanic.
Playing a Hidden monster from your hand is considered a summon unless otherwise stated.

✨ Details on Card Types

Main Card types: Represent the different groups of cards in this game, a card must have at least one of these: Monster, Trap, Spell, Rule, Token, Emblem.

Secondary Card types: Are used in conjunction to the Main types to offer different gameplay options from a mechanical standpoint on how that card is played or interacts: Fusion, Ritual, Alter, Integration, Divine, Hierarchy, Equip, Continuous, Persist, Setup, Field Setup, Duelist Setup, Challenge Setup, Symbol.

Divine types (also known as “Pantheons”): Are a way to group Divine cards that are related to each other and may have built-in synergy: Palace God, Storm Guardian, Wicked God, etc.

Primary Monster Types: Refer to what the monster actually is.

Angel: (Equivalent to “Fairy”) Sprites, angels, fairies, holy beings.
Aquatic: (Equivalent to “Fish”, “Sea Serpent” and partially to “Aqua”). All kinds of water monsters or creatures whose natural habitat is water, without being themselves some sort of embodiment of water itself.
Avian: (Equivalent to “Winged Beast”). Related in some ways to birds either by being a type of them or having some bird-like feature, specially wings.
Beast: Terrestrial beasts of all kinds.
Cosmic: Related to space and the unknown, including alien-like entities, space machines or otherworldly creatures.
Demon: (Equivalent to “Fiend”). All types of Demons and demon-like creatures.
Dinosaur: Big and smol dinos.
Dragon: (Equivalent to “Dragon” and “Wyrm”) A mix of Eastern and Western conceptions of dragons.
Elemental: (Equivalent to “Rock”, “Pyro”, “Aqua”, “Thunder”). Elementals are concepts made into living forms, be it generic like water, lightning, fire or earth or more specific ones or abstract ones. They are usually referenced with the Attribute.
Esper: (Equivalent partially to “Psychic”). Paranormal abilities for humanoid monsters sometimes mixed with electronics and some degree of technology, including cybernetic enhanced creatures.
Frost: Cold-based creatures of all types, related to ice and frost.
Illusion: Creatures related to mirages, dreams and apparitions.
Insect: Insects of all sizes. This categorization also includes arachnids, scorpions and other arthropods too.
Machine: Broad type that refers to mechanical constructs, machines and technology in general.
Plant: Nature based plant-like creatures, be it small ones or overgrown ones.
Reptillian: Reptiles in general or reptile-like creatures.
Spellcaster: Individuals who naturally wield the power of magic, for example magicians, sorcerers and wizards.
Support: Non-warrior-like and non-spellcaster-like humanoids. A more “mentally” type of humanoid monster or someone who assists allies in different ways.
Undead: (Equivalent to “Zombie”). Group of beings that includes mummies, zombies, skeleton, ghosts, apparitions, etc. This also includes certain supernatural beings like Vampires.
Warrior: Super broad type that refers to humanoid fighters and combatants in general.

Secondary Monster Types: Refer to what the monster can do or is affected by.

Absorption: Is able to absorb into itself other creatures or souls.
Blessed: Is being favored by a god-like entity.
Burrowing: Is able to dig and go beneath the ground with ease.
Dampened: Is currently soaked in water.
Fireblast: Is able to attack with a large display of fire.
Flying: Is able to properly fly (not only float or barely move in the air).
Poisoned: Is affected by poison or venom.
Protector: Is able or dedicated to protect others.
Regeneration: Is able to regenerate wounds or even reverse its own death.
Sealed: Is sealed through magic or other means.
Thunderblast: Is able to attack with electricity or magic of the electric type.

Alter Monster Types: A specific group of types that is exclusive to Alter Monsters.

Ascended: A monster that embraces the holy power to its fullest and is transformed by it.
Eldritch: A monster transformed in a living horror through unnatural powers beyond human comprehension.
Metalized: A monster covered in an alloy that turns a biological being into a metallic/technological version of itself.
Swarm: A group or copies/clones of a single monster, represented as multiple monsters on the very same card.
Timeshifted: An older or younger version of a particular monster, in a different point in time.
Toon: A “cartoonified” version of a regular monster.
Zombie: A non-undead monster that comes back to life as a zombie and is now reanimated after death.

🤝 Multiplayer Rules

A Team Duel is what happens when more than two opposing players take part in a duel. There are three types: Tag Duels, Boss Duels and Battle Royale Duels.

The main difference between regular duels and Team Duels is that a Rotation of turn order must be defined during the Setup Phase, based on the type of team duel used and the number of players. As a general rule, the Rotation order always iterates between teams first, and then further than teams it iterates between each player of the team.

Only the last player in the Rotation is allowed to declare an attack in the first round of a Team Duel.

Unless otherwise stated the life points and gameplay zones (field, graveyard, hand, main deck, extra deck, rule zone) belong to each player and behave like in a regular duel.

Tag Duels are 2v2 duels of teams fighting each other:

The Rotation is: TeamAPlayer1 → TeamBPlayer1 → TeamAPlayer2 → TeamBPlayer2.
If one player is defeated the whole team is defeated.
Players in a team have a shared field of 10 Frontrow and 10 Backrow.
Even in the shared field each player controls their corresponding zones and cards.
Teammates can reveal some secret information between them in the shared areas (face-down cards) but not in the private areas (like hand and extra deck cards).
Your teammate can allow you to use their cards during your turn for summoning conditions, but not for attacks, battle position changes or movement.

Boss Duels are a “one vs many” duel, where the “many” join forces into a team:

The Rotation is: SoloPlayer → TeamPlayer1 → SoloPlayer → TeamPlayer2…
The team players share LP and the board (field, graveyard and rule zone) but each still has their own Deck and Extra Deck.
The team players collectively control the zones and cards in that side of the field, except the cards in the Rule Zone that are still individually controlled.
The team players must also agree to play a single Field Setup card, not one for each.

Battle Royale Duels are free-for-all duels of 3+ participants without specific allies, everyone is technically considered an opponent here:

The Rotation is: Player1 → Player2 → Player3…
If a player is defeated: the rotation adjusts removing that player. Cards owned by that player that are controlled by other players stay in the field.
Once per round, a player can redirect an attack that targets a monster controlled by another player to a monster they control (that is able to move), and if it does, the attacking monster cannot be destroyed by that battle and the controller of that attacking monster takes no damage from that battle.
A player can allow you to use their cards during your turn for summoning conditions, but not for attacks, battle position changes or movement.
A player can join a Battle Royale at any point by taking damage equal to half of its starting LP, and inserting themselves as next in the rotation.
After at least one player is defeated, at any point the remaining players can unanimously declare that the duel is over (and they are considered the winners) if they dont want to keep dueling eachother.

🔧 Deckbuilding

Each player needs a Main Deck with exactly 30 cards and an Extra Deck with up to 20 cards. Your Main Deck can have Spell Cards, Trap Cards and Normal Monster Cards. Your Extra Deck can have Extra Deck Monster Cards and Rule Cards.

There are certain cards that have restrictions on how many of them you are allowed to include in your deck, check the Restricted List for more information about this.

Duelist Setup Rule cards allow you to have in your decks any card listed in its “Cardlist” (in the quantity it specifies if its more than one) ignoring the Restricted List limitations in deckbuilding.

(Optional) If you want, you can add one or more Challenge Setup Rule cards to your deck to spice up a bit your deckbuilding skills, but this is entirely optional.

Note: Additional deckbuilding limitations may be needed depending on the match-up or the players. Kingdom Duels is by nature an unbalance game so feel free to adjust the banlist/restrictions if you feel like it in the interest of a more fair gameplay experience.

TL;DR

Regular Yugioh but…

2000 LP. Starting hand of 5, draw 1 each turn (even in the first turn).
The Board has 5 monster zones and 5 spell/trap zones. No link/pendulum/field zones.
Rule Cards exist (which are Extra Deck cards that change how the game is played).
Setup Rule cards must be played in the Setup Phase: Your Field Setup define your terrains. You can change up to 2 cards from your starting hand with cards from your Duelist Setup “cardlist”.
Terrain Markers exist (they go between the monster zones and the cards). They can give effects and “Field Power Bonus” to monsters on them.
You can summon normal monsters of any Level without a tribute.
You can play monsters in face-up DEF. You can’t Set monsters (you “Hide” them instead).
You can only Hide monsters in face-down ATK or face-down DEF if an effect lets you.
No direct attacks. Can only attack once per battle phase. Attacks can be redirected.
Instead of banish there is “erode” which is a more permanent removal.
If you are repeatedly idle by not playing monsters you’ll lose.
Normal Spells are usually quick speed (Equip and Continuous are slow speed).
Traps are (mostly) triggered automatically.
Extra Deck monsters include: Fusions, Rituals, Alters, Integrations.
There are Spell-Trap-Monster combinations and even Divine cards.