Activate Fire Nation Palace's second ability by paying {1}{R} and tapping it, giving Hellkite Charger firebending 4 until end of turn.
Declare Hellkite Charger as an attacker, triggering it and its firebending ability twice.
Resolve both Hellkite Charger firebending triggers, adding eight {R}.
Resolve the first Hellkite Charger trigger, choosing not to pay.
Resolve the second Hellkite Charger trigger, causing you to pay {5}{R}{R} to untap all attacking creatures and to get an additional combat phase after this one.
Repeat from step 2.

Infinite combat phases

Infinite red mana

Hellkite Charger

Fire Nation Palace

Windcrag Siege

Declare Hellkite Charger as an attacker, triggering it and Avatar Roku twice.
Resolve both Avatar Roku triggers, adding twelve {R}.
Resolve the first Hellkite Charger trigger, choosing not to pay.
Resolve the second Hellkite Charger trigger, causing you to pay {5}{R}{R} to untap all attacking creatures and to get an additional combat phase after this one.
Repeat.

Infinitely powerful creatures you control until end of turn

Avatar Roku, Firebender

Declare Altaïr as an attacker, triggering its ability twice.
Resolve a Altaïr trigger, exiling Éomer from your graveyard with a memory counter on it and creating a tapped and attacking copy of Éomer.
Resolve the other Altaïr trigger, creating a tapped and attacking copy of Éomer.
Put either Éomer token into your graveyard due to the legend rule, triggering the other Éomer token, causing you to untap all creatures you control and to get an additional combat phase after this one.
At the end of your combat phase, Altaïr triggers, causing you to exile the Éomer token.
Repeat each combat phase.

Combos with "Windcrag Siege"