Labyrinth Builder decks are frequently used for getting high score against Legendary Duelists (LDs). Many of LDs don't have monsters can beat your Labyrinth Wall (3000 DEF), so you can easily stall turns with it. On the final turn when your deck is 0, you'll finish the duel with Union Attack combo or Piranha combo to achieve Over 9,999 Damage.
Labyrinth Builder Lockdown
Using Paradox Brothers' Labyrinth Builder skill, you can special summon Labyrinth Wall. Since it has pretty high defense of 3000, most Legendary Duelists can't deal with it. Note that you need to shuffle 2 cards from your hand to the deck to use the skill.
Dimension Gate for Perfect Lockdown
This deck relies quite heavily on getting Dimension Gate early in the duel. If you don't get it in your starting hand, use your draw cards or set A Cat of Ill Omen to get it from your deck. Once you have it, activate the skill and send unused cards into the deck. Set the dimension gate and activate it to banish the labyrinth.
Once you have the labyrinth and banished it, you can simply keep using draw cards to quickly lower the number of cards in your deck.
Use Crystal Seer's effect at least once. By sending an unused card to the bottom of the deck, it will ensure that you don't get essential card as the last draw.
Make sure to not use the draw cards so that you go from more than 2 or more cards left in your deck straight to 0. Having only 1 card left in your deck is important since the AI will decide to not attack you at all, allowing you to normal summon Vassal/Piranha freely. Note: This only works if AI has more cards in his deck than you, which is why you have to keep using your draw cards so you end up lower than your opponent.
If you are using Twin-Headed Thunder Dragon with Shield & Sword: Fusion summon the thunder dragons and use storm to special summon the labyrinth in attack position. Use shield & sword, then secret pass and double union attack onto Vassal before attacking directly.
Paradox Bros' Labyrinth Builder skill is necessary. If you have not obtained this skill yet, use Elements Unite decks to beat Legendary Duelists Lvl 40 to find the skill from post-duel treasure chests.
Labyrinth Builder Shuffle 2 cards from your hand into the Deck to create "Labyrinth Wall" on your side of the field. This skill can only be used once per Duel.