Magic: The Gathering

The Arcane Labyrinth — Rules Reference (V6)

V6 Foreword and Changelog

Please reach out at arcane-labyrinth@pm.me if you have any feedback or notice any errors in the rules. Thank you!

Last updated 2025-12-31

2025-12-31 V6 Draft 2 Released

This draft addresses some inconsistencies in the rules and tries to further clarify some points.

2025-12-30 V6 Draft 1 Released

Version 6 of the Arcane Labyrinth ruleset aims to tweak and streamline the gameplay experience of the format. Various rules have been adjusted and tweaked for balance. Additional difficulity modifiers have also been added.

I. Overview & Objective

The Arcane Labyrinth is a high-stakes, solo "Dungeon Crawl" format for Magic: The Gathering. You control a single Hero (Avatar) and a deck of spells/creatures representing your party (the Vanguard).

• The Goal: Survive 100 rooms (cards) of an automated, escalating nightmare and defeat the Final Boss located at the bottom of the Labyrinth deck.
• The Enemy: The Labyrinth is an automated deck that plays itself. It follows strict behavioral rules to attack, cast spells, and grow in power.
• The Stakes: If your Hero’s Life hits 0, the game is over.

When the player attacks the Labyrinth directly, the Labyrinth mills cards from its deck equal to the amount of damage the player would do.

The player wins the game after getting to the bottom of the Labyrinth deck and defeating the final boss. If the boss is defeated and there are no cards left in the deck, the player wins.

Note: The boss always starts the game at the bottom of the deck. Shuffling the Labyrinth deck excludes shuffling the boss, it stays on the bottom. Thematically, the boss is the final room in the dungeon, and thus has a fixed position in the deck.

II. Deck Construction and Setup

1. The Hero (Avatar)

• Selection: Choose 1 Legendary Creature or Planeswalker. This is your Avatar.
• Start: It begins the game on the battlefield. It has no mana cost.
• Health: You have 20 Life. Damage to the player is damage to the Hero.
  • Note: Effects that target "Player Life" target Hero HP.

2. The Hero Deck (The Vanguard)

• Size: 60 Cards.
• Construction: Standard construction rules apply (max 4 copies of a card).
• Restriction: Maximum 1 Artifact card allowed in the main deck. (This encourages reliance on the Secret Shop).
• Banned: Cards with "You win the game" effects are disqualified 1.

3. The Secret Shop Deck

• Size: 10+ Artifact Cards.
• Role: Represents equipment and items you can buy during the run. This is considered an attribute of the Hero's kit, not the Labyrinth, and should synergize with the Hero’s deck.

4. The Labyrinth Deck (The Dungeon)

• Size: 100 Cards exactly.
• Composition:
  • Below card figures are guidelines. With the exception of the Mana color rules on the line below, and 5 legendary creatures, you are free to compose this deck however you’d like.
  • Lands: ~15 (Must include at least 1 Land for every color produced by the deck).
  • Creatures: 55–65.
  • Spells: 20–30.
  • Bosses: Must contain exactly 5 Legendary Creatures (or "Rare" equivalents if Legendaries are unavailable) distributed throughout the deck.
• The Final Boss: One specific Legendary Creature must be placed at the very bottom (card 100) of the deck.

III. Playing the Game

The Preparation Phase

Before the Labyrinth awakens, you have time to prepare your defenses.

1. Safe Turns: You receive 3 Safe Turns.
2. Actions: You may play lands, cast spells, and build your board state.
3. Restrictions:
   • You cannot conduct an Attack Phase (you cannot attack the Labyrinth directly).
   • You can use burn spells or mill effects to damage the Labyrinth deck.

The Dungeon Phase (The Game Loop)

Starting on Turn 4, the Labyrinth awakens.

1. The Labyrinth Draw Step

The Labyrinth reveals the Top 2 Cards of its library every turn. Resolve them sequentially:

• A. Lands:
  • Enter the battlefield, and immediately go to your land pool untapped. They can be used immediately.
  • Effect: Revealing a Land triggers the Shop Phase at the end of this Labyrinth turn, before the players turn.
• B. Creatures:
  • Enter with Haste.
  • Must Attack each turn if able (they never block).
• C. Spells & Traps:
  • Resolve immediately.
  • The Labyrinth ignores "Additional Costs" (e.g., sacrifice requirements are skipped unless mandatory for the effect to function) of a card.
  • Ambiguity Rule: If a card has multiple modes (e.g., "Choose one..."), roll a die to determine which effect is selected.
  • Targeting Rule: If a spell requires a target (e.g., "Destroy target permanent"), randomly determine the target among valid player permanents using a die roll.
• D. Global Enchantments/Artifacts:
  • Apply globally to the Labyrinth’s board until removed by the player.

The "Golden Rules of the Labyrinth"

The Labyrinth always plays at least 2 cards per turn. If a player effect prevents a draw/play, the Labyrinth ignores it. If the Labyrinth deck is empty and the final boss has been cleared, the player wins.

• The Immunity Rule: The Hero cannot leave the battlefield. Effects that would destroy, exile, or bounce the Hero instead cause the Hero to become Exhausted (see Hero Exhaustion in the following section).
• Targeting Rule: If a spell requires a target (e.g., "Destroy target permanent"), randomly determine the target among valid player permanents using a die roll.
• The Ethereal Hand: The Labyrinth has no hand. If a spell or ability would return a Labyrinth card to its hand, put that card on the top of the Labyrinth Library. If a spell causes the Labyrinth to discard, mill that many cards instead.

Additional Labyrinth Rules:

• Labyrinth cards are placed on the Stack when revealed.
• Players may cast Instants and activate abilities in response to Labyrinth cards.

Combat & Hero Mechanics

1. Attacking

Labyrinth creatures attack automatically. The player can, as in standard Magic, allocate specific creatures to specific attackers as part of blocking, and can choose to let the attack go straight to their hero.

2. Blocking with the Hero

Your Hero (Avatar) is a valid blocker.

• Successful Block: If Hero Toughness > Attacker Power, you take 0 damage to your Hero Health.
• Hero Exhaustion (The "Downed" State):
  • Trigger: If the Hero's Toughness is reduced to 0 or less (via combat damage or -X/-X effects), or if they block a Deathtouch creature, the Hero becomes Exhausted.
  • Effect:
    • The Hero is treated as Exiled until your next Upkeep.
    • Passive abilities cease to function.
    • They cannot block.
    • Any tokens, counters, or stateful effects on your hero are removed.
    • Crucial: You generally still take Hero Health damage from unblocked attackers while Exhausted. Eg you cannot Exile your hero in perpetuity to become invulnerable.
  • Recovery: At the start of your next Upkeep, return the Hero to the battlefield (Reset to base stats).

The Secret Shop

Trigger: If the Labyrinth played a Land this turn, the Shop opens at the End Step of the Labyrinth’s turn.

1. Reveal: Reveal the top 3 Artifacts from your Shop Deck.
2. Purchase: You may buy an artifact by sacrificing lands equal to its Mana Value.
   • Colored Costs: You must sacrifice lands capable of producing the required colors.
   • The item goes to your Hand (you must cast/equip it normally).
3. Scrap: Unpurchased cards go to the bottom of the Shop Deck.

Random Encounters

Every 3rd Turn (Turns 3, 6, 9...), roll a D20 before the Draw Phase27:

The Final Boss

When the bottom card (100th card) is reached:

1. Equipment: The Boss enters the battlefield equipped with the most expensive Artifact remaining in the Shop Deck (equipped for free).
2. Scaling Buffs:
   • If reached in < 10 Turns: Boss gets +10/+10.
   • If reached in < 15 Turns: Boss gets +5/+5).

IV. Rule Reference

This section aims to be a reference for specific rules and resolutions. It should serve to clarify potentially ambiguous behavior/interactions and to guide players around the specifics of the format.

Labyrinth

• The Lab. never spends/uses mana. Any lands it top decks go immediately into the player land pool, exactly as if they'd be played by the player.
• The Lab. never pays 'additional costs' for cards
• The Labyrinth has no hand. Interactions that return cards to the Labyrinth's hand instead return it to the top of the Labyrinths deck. Spells that reveal the Labyrinth's hand have no effect.
• When the Labyrinth top decks a card with an effect, it's placed on the stack. The Player receives priority to respond and if no response is made the card is resolved.
• The Labyrinth boss card cannot be milled from the deck, and exists outside of the deck until the deck has been drawn down and it can be played as the final card in the deck.

Player/Hero/Vanguard

• The player starts the game with 3 consecutive safe turns. Safe turns have the following characteristics:
• • Safe turns have no combat phase. Players cannot directly attack during a safe turn.
• • Safe turns otherwise resemble regular turns. The player can draw a card, play spells, etc
• • During safe turns the Labyrinth does not untap, draw, or act.

Keyword Resolution

Labyrinth Interaction Rules (Keywords)

• Life Gain: If the Labyrinth would gain X life, instead shuffle X cards from the top of the Labyrinth graveyard back into the Labyrinth deck. The cards go back into the deck in the order the entered in. Eg. If I gain 1 life I take the top 1 card from the graveyard and shuffle back into the deck.
  • Anti-Loop: If this happens >2 times to a single card, Exile that card instead.
• Dread/Manifest: Play the card face-down (2/2). Flip it face-up during the next Upkeep
• Deathtouch: If a Hero blocks a Deathtouch creature, the Hero is Exhausted.
• Return To Hand: If the player plays a card with the effect of “Return target to hand” against the Labyrinth, the target goes to the top of the Labyrinth’s library. If the Labyrinth uses a “Return to hand” effect on itself, it goes to the top of the Labyrinth’s library.
• Devour:
  • Roll a d6. If the result is >3 the unit devours.
  • Roll another d6. Devour this many units (or as many as you can)

Hero Interaction Rules (Keywords)

• Deathtouch: If a Hero blocks a Deathtouch creature, the Hero is Exhausted.
• Exile: The hero is Exhausted
• Sacrifice: The hero is Exhausted

V: Optional Rules (Difficulty Mods)

These additional gameplay tweaks can make underwhelming Labyrinth decks pack a bit more of a punch. Additionally if your hero deck is a particularly good counter to a specific Labyrinth deck, these can help increase the challenge a bit.

• Entropy Draw (Scaling Difficulty): If the Player controls 10+ creatures OR a creature with Power 10+, the Labyrinth draws 3 cards per turn.
• Desperation Mode: If the Labyrinth deck has <50 data-preserve-html-node="true" cards remaining, all Labyrinth creatures gain Trample (prevents chump-blocking).