Ponix + any FIRE monster

You can push the limits of what the Fire King engine is "supposed" to do, by Xyz Summoning Garunix Eternity, Hyang of the Fire Kings during your turn, then use its effect in combination with Fire King Sanctuary to make Hyang destroy itself, to further set up and extend.

This leads to an unassuming board ending on a Level 8 Fire King Courtier Ulcanix, with Legendary Fire King Ponix and Fire King High Avatar Kirin in hand - however it lets you make a 4-material Hyang during the opponent's turn, if you so choose!

In the video below, we will use Flamvell Guard as a placeholder for any FIRE monster. In real duels, this can be any card in your deck that fulfills this requirement.

This combo plays into Nibiru, the Primal Being - read the section at the end for more details on how to recover.

Under Mulcharmy Fuwalos, your opponent draws 2 cards.

Steps

  1. Normal Summon Legendary Fire King Ponix.
  2. Activate Ponix: add Fire King Sanctuary from your Deck to your hand.
  3. Activate Sanctuary: place Fire King Island in the Field Zone.
  4. Activate Island: destroy Ponix, then add Sacred Fire King Garunix from your Deck to your hand.
  5. Activate Sacred: Special Summon it from your hand.
  6. Activate Sacred again: destroy Fire King Courtier Ulcanix in your Deck.
  7. Activate Ulcanix: Special Summon Fire King High Avatar Garunix from your Deck.
  8. Xyz Summon Garunix Eternity, Hyang of the Fire Kings.
  9. Activate Hyang, detaching Sacred; target Island to destroy it.
    • At resolution, use Sanctuary's effect to destroy Hyang instead.
  10. Activate Hyang again; Special Summon Ulcanix from the GY.
  11. Activate Ulcanix: destroy the FIRE monster in your hand, add Fire King High Avatar Kirin from your Deck to your hand, then declare on resolution that Ulcanix is now Level 8.
  12. Pass turn.

Opponent's turn

  1. In the Standby Phase, activate Ponix: add it from the GY to your hand.

This line does have caveats - wasting a Hyang can potentially limit your grind game potential in Pot of Extravagance lists - like the one this guide is based on - and the FIRE monster used for combo is not recovered in any meaningful way.

That said, the ability to set up a 3-4 material Hyang (depending on whether you want to leave High Kirin on the field to be destroyed) allows for plenty of power and flexibility.

Also, by having High Kirin and Ponix in hand, you are less vulnerable to board breakers like Raigeki, Lava Golem, etc, and you can choose when to start interrupting your opponent.

If Nibiru hits
Regardless of where your opponent chooses to activate Nibiru, you will only lose Ulcanix, allowing you to still play just fine, but it reduces your follow-up on turn 3.
Destroying Island
It is entirely plausible to NOT protect Island at step 9, and let Hyang actually destroy it. This would lead to exactly the same endboard due to Island destroying Hyang, letting you continue as usual.

The downside is that it would substantially hurt your grind game, as you no longer have access to Island's effects.

The upside, however, is that it would remove a liability from the board - the opponent might try to remove Island through non-destruction effects, causing your board to blow up - so in certain matchups this could be useful!