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 Chain Lightning by paying {R}, targeting Crystalline Crawler.
Resolve Chain Lightning, putting three +1/+1 counters on Crystalline Crawler due to Vigor and choosing to pay {R}{R} to create a copy of Chain Lightning targeting Crystalline Crawler.
Holding priority, activate Crystalline Crawler's first ability twice by removing two +1/+1 counters from it, adding {R}{R}.
Repeat from step 2.

Combos with "Chain Lightning"