Cast a copy of Seething Song by paying {2}{R}.
Displacer Kitten triggers, blinking Blazing Firesinger. It'll enter prepared due to its effect.
Resolve Seething Song, adding {R}{R}{R}{R}{R}.
Repeat.

Infinite creature ETB

Infinite creature LTB

Infinite magecraft triggers

Infinite red mana

Infinite storm count

Blazing Firesinger // Seething Song

Displacer Kitten

Cast a copy of Seething Song from exile by paying no more than {1}{R}, adding {R}{R}{R}{R}{R}.
When you cast that spell, Storm-Kiln Artist triggers, creating a Treasure token.
Activate the Treasure token by tapping and sacrificing it, adding one mana of any color.
Activate Emiel the Blessed by paying {3}, blinking Blazing Firesinger, which enters prepared.
Repeat.

Infinite artifact ETB

Infinite artifact LTB

Emiel the Blessed

Storm-Kiln Artist

Activate Ashnod's Altar by sacrificing Goblin Glasswright, adding {C}{C}.
Cast a copy of Seething Song from exile by paying {2}{R} and unpreparing Blazing Firesinger.
When you cast that spell, Extus triggers, returning Goblin Glasswright from your graveyard to your hand.
Resolve Seething Song, adding {R}{R}{R}{R}{R}.
Cast Goblin Glasswright by paying {1}{R}.
Goblin Glasswright enters prepared.
Activate Ashnod's Altar by sacrificing Blazing Firesinger, adding {C}{C}.
Cast a copy of Craft with Pride from exile by paying {R} and unpreparing Goblin Glasswright.
When you cast that spell, Extus triggers, returning Blazing Firesinger from your graveyard to your hand.
Resolve the copy of Craft with Pride, creating a Treasure token.
Cast Blazing Firesinger by paying {2}{R}.
Blazing Firesinger enters prepared.
Repeat from step 2.

Infinite Treasure tokens

Infinite colored mana

Infinite death triggers

Infinite creature sacrifice triggers

Infinite artifact sacrifice triggers

Infinite artifact tokens

Extus, Oriq Overlord // Awaken the Blood Avatar

Goblin Glasswright // Craft with Pride

Ashnod's Altar

Activate Kiki-Jiki by tapping it, copying Blazing Firesinger. It'll enter prepared due to its effect.
Cast a copy of Seething Song by paying {2}{R}.
The Vision and Scarlet Witch triggers as well as Hematite Talisman.
Resolve the Vision and Scarlet Witch trigger, adding {R} and putting a +1/+1 counter on it.
Resolve the Hematite Talisman trigger, causing you to pay {3} to untap Kiki-Jiki.
Resolve Seething Song, adding {R}{R}{R}{R}{R}.
Repeat.

Infinite creature tokens with haste

Infinite +1/+1 counters on a creature

Kiki-Jiki, Mirror Breaker

Hematite Talisman

The Vision and Scarlet Witch

Activate Orthion's second ability by paying {6}{R}{R}{R}, creating five token copies of Blazing Firesinger that enter prepared.
Cast a copy of Seething Song by paying {2}{R}.
Chakram Retriever triggers, untapping Orthion.
Resolve the copy of Seething Song, adding {R}{R}{R}{R}{R}.
Repeat from step 2 four additional times. You may untap other creatures in step 3 as desired.
Repeat from step 1.

Infinite mana creatures you control can produce

Infinite untap of creatures you control

Orthion, Hero of Lavabrink

Chakram Retriever

Activate Kiki-Jiki by tapping it, copying Blazing Firesinger. It'll enter prepared due to its effect.
Cast a copy of Seething Song by paying {2}{R}.
Thousand-Year Storm and Hematite Talisman trigger.
Resolve the Thousand-Year Storm trigger, copying Seething Song for each instant and sorcery cast before it this turn.
Resolve all copies of Seething Song, adding {R}{R}{R}{R}{R} for each copy.
Resolve the Hematite Talisman trigger, causing you to pay {3} to untap Kiki-Jiki.
Resolve the original Seething Song, adding {R}{R}{R}{R}{R}.
Repeat.

Thousand-Year Storm

Combos with "Blazing Firesinger // Seething Song"