Entity

"Entity" is a series of cards introduced in Legacy of the Valiant. The series is based on H. P. Lovecraft's Cthulhu Mythos, and comprises three archetypes: "Elder Entity" Fusion Monsters, "Old Entity" Synchro Monsters, and "Outer Entity" Xyz Monsters.

Playing style
The Deck is based around the synergy between the archetype's Fusion, Synchro and Xyz Monsters. The main purpose of the deck is to overlay a Fusion Monster and a Synchro Monster to Xyz Summon "Outer Entity Nyarla", who is then used to Summon "Outer Entity Azathoth", who can use its effect to destroy all cards the opponent controls if it has all three monster types as its Xyz Materials.

The simplest way to Summon "Azathoth" and be able to use its effect is to use "Instant Fusion" to Summon "Elder Entity Norden" and use its effect to revive "Old Entity Chthugha" or "Old Entity Hastorr", then overlay them into "Nyarla" and then "Azathoth". Because "Azathoth" needs a Fusion Monster, Synchro Monster, and Xyz Monster as its Xyz Materials to use its effect, and needs to detach one to activate it, it will usually only be able to use that effect once; "Xyz Override" and "Xyz Unit" can be used to allow "Azathoth" to use its effect multiple times.

Reliance on "Norden" for this Deck is important, as it can allow the Summon of "Azathoth" single-handedly by Special Summoning a Level 4 Synchro Monster so "Nyarla" can be Summoned. "Re-Fusion" and "Call of the Haunted" are useful to continue Summoning "Norden" and thus keep reusing its effect. "Norden" can also be Summoned by its normal method, using "Polymerization" to fuse two Synchro and/or Xyz Monsters, as the Deck should not have problems getting those Fusion Materials into play at once, and if a Synchro Monster is used as a Fusion Material, "Norden" can revive it once Summoned. "Fusion Substitute" or "Flash Fusion" can be used instead of "Polymerization", since any monsters to be fused will not come from the hand. Other than "Norden", "Cthugha" is another important card due to the draw power it provides the player when repeatedly used for Xyz and Fusion Summons.

"Norden" only needs "Instant Fusion" or "The Unspeakable Trapezohedron" to be Summoned, which can be worked into any Deck, and "Nyarla" is best used with "Cthugha" or "Hastorr" as its Xyz Materials. Thus, any main Deck theme that can reliably Summon Level 4 Synchro Monsters will work as support for the series, as long as the mentioned Spell Cards for Summoning "Norden" are also included. One potential Deck for use is a Warrior-Type Deck. "Marauding Captain" and "Junk Synchron" allow for the quick summoning of monsters to set up for the summoning Level 4 Synchro Monsters and Rank 4 Xyz Monsters. The Deck's access to "Reinforcements of the Army" and "The Warrior Returning Alive" also increases flexibility depending on what type of monster the player needs. "Doppelwarrior" and "Tuningware" are also useful in getting Level 1 and/or Level 2 monsters into play for Synchro Summons. "Synchro Fusionist" is an excellent support card for this deck, allowing the searching of "Instant Fusion" and "Re-Fusion."

Beyond this, Level 3 and 4 monsters that can change their Levels are useful, if the player needs a Level 3 monster to go with a Tuner for a Synchro Summon, or a Level 4 monster for an Xyz Summon.

Weaknesses
The Deck's major problem is consistency—the unusual combination of cards needed to support so many different summoning methods means the player may have a hand full of cards that do not work together to accomplish the Deck's objective. The reliance on quickly performing these Summons also makes the Deck bad for hand advantage, and their momentum can be halted if the opponent is able to stop their combo in progress. The size of the Extra Deck is also a problem—the player is unlikely to have much room for monsters outside the "Entity" theme, and thus their deck may lack versatility. "Daigusto Emeral" is a useful tech option to return the player's cards to the Extra Deck in a pinch, allowing the player to run fewer copies of them and include more Synchro and Xyz Monsters that can support the deck.