Cast Cursed Mirror by paying {2}{R}, choosing to have it enter the battlefield as a copy of Storm-Kiln Artist until end of turn.
Cast Chain Lightning by paying {R}, targeting Brash Taunter.
Storm-Kiln Artist and Cursed Mirror each trigger, creating two Treasure tokens.
Activate both Treasure tokens by tapping and sacrificing them, adding {R}{R}.
Resolve Chain Lightning, dealing 3 damage to Brash Taunter, and causing you to pay {R}{R} to copy Chain Lightning, targeting Brash Taunter.
Brash Taunter, Storm-Kiln Artist, and Cursed Mirror each trigger.
Resolve the Brash Taunter trigger, dealing 3 damage to an opponent.
Resolve the Storm-Kiln Artist and Cursed Mirror triggers, creating two Treasure tokens.
Repeat from step 4.

Infinite damage

Infinite magecraft triggers

Brash Taunter

Storm-Kiln Artist

Chain Lightning

Cursed Mirror

Cast Chain Lightning by paying {R}, targeting Brash Taunter.
Storm-Kiln Artist triggers, creating a Treasure token.
Activate the Treasure token by tapping and sacrificing it, adding {R}{R}.
Resolve Chain Lightning, dealing 3 damage to Brash Taunter, and causing you to pay {R}{R} to copy Chain Lightning, targeting Brash Taunter.
Brash Taunter and Storm-Kiln Artist each trigger.
Resolve the Brash Taunter trigger, dealing 3 damage to an opponent.
Resolve the Storm-Kiln Artist trigger, creating a Treasure token.
Repeat from step 3.

Goldspan Dragon

Activate Mirage Mirror by paying {2}, causing it to become a copy of Storm-Kiln Artist until end of turn.
Cast Chain Lightning by paying {R}, targeting Brash Taunter.
Storm-Kiln Artist and Mirage Mirror each trigger, creating two Treasure tokens.
Activate both Treasure tokens by tapping and sacrificing them, adding {R}{R}.
Resolve Chain Lightning, dealing 3 damage to Brash Taunter, and causing you to pay {R}{R} to copy Chain Lightning, targeting Brash Taunter.
Brash Taunter, Storm-Kiln Artist, and Mirage Mirror each trigger.
Resolve the Brash Taunter trigger, dealing 3 damage to an opponent.
Resolve the Storm-Kiln Artist and Mirage Mirror triggers, creating two Treasure tokens.
Repeat from step 4.

Mirage Mirror

Cast Chain Lightning by paying {R}, targeting Brash Taunter.
Storm-Kiln Artist triggers, creating two Treasure tokens.
Activate both Treasure tokens by tapping and sacrificing them, adding {R}{R}.
Resolve Chain Lightning, dealing 3 damage to Brash Taunter, and causing you to pay {R}{R} to copy Chain Lightning, targeting Brash Taunter.
Brash Taunter and Storm-Kiln Artist each trigger.
Resolve the Brash Taunter trigger, dealing 3 damage to an opponent.
Resolve the Storm-Kiln Artist trigger, creating two Treasure tokens.
Repeat from step 3.

Xorn

Jolene, the Plunder Queen

Cast Lightning Storm by paying {1}{R}{R}, targeting either copy of Stormchaser Drake.
Stormchaser Drake triggers, which due to Abundance causes you to reveal cards from the top of your library until you reveal a land card and put it into your hand.
Activate Lightning Storm by discarding a land card, putting that land card on the bottom of your library due to Wheel of Sun and Moon.
Resolve the Lightning Storm ability, putting two charge counters on it and changing the target to the other copy of Stormchaser Drake.
Repeat from step 2.
Once Lightning Storm has an arbitrarily large number of charge counters, activate it by discarding a land to change its target to any other target of your choosing to deal infinite damage to that target.

Infinite self-discard triggers

Infinite damage to one opponent

Lightning Storm

Stormchaser Drake

Wheel of Sun and Moon

Abundance

Vesuvan Shapeshifter

At the beginning of your combat phase, Saheeli triggers, causing you to pay {E}{E}{E} to create two token copies of Aethertide Whale with haste.
When the Aethertide Whale tokens enter the battlefield, they trigger, causing you to get twelve {E}.
Declare Lightning Runner as an attacker, triggering its ability, causing you to get {E}{E} and then pay eight {E} to untap all creatures you control and to get an additional combat phase after this one.
Repeat each combat phase.

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