The Fire King Sanctuary

Garunix Eternity, Hyang of the Fire Kings Rank 8 FIRE Pyro 2+ Level 8 monsters If this card is Xyz Summoned: You can destroy all other monsters on the field. You can detach 1 material from this card, then target 1 Spell/Trap on the field; destroy it, and if you do, this card gains 500 ATK. If this card is destroyed while it has material: You can Special Summon "Fire King" monsters from your GY, up to the number of materials this card had. You can only use each effect of "Garunix Eternity, Hyang of the Fire Kings" once per turn. ATK 3000 | DEF 2000

The big boss of the archetype, and our only Extra Deck monster.

If this card is Xyz Summoned, you can destroy all other monsters on the field, which is immensely powerful. Coupled with Fire King Sanctuary, you can do this during your opponent's turn, potentially shutting their strategy down completely, or at least leaving them in a weaker position.

The Spell/Trap destruction effect, with the associated ATK boost, is helpful but comes up rarely, as you usually will prefer to preserve the materials so the third effect is more explosive. You can use it in certain situations to enable an OTK, by attempting to destroy Fire King Island and using Sanctuary's effect to destroy Hyang instead - see the [Hyang Self-Destruction OTK] pattern.

Yes, you read that right - by destroying Hyang with all its materials still attached, you can Special Summon that many Fire Kings from the GY - a game-changing effect in the proper circumstances. We'll discuss some OTK combos later on, which make use of this effect to immediately put out 8000 or more damage.

You can run 1-3 copies, depending on how often you think Sanctuary's effect will come up.