You have another instant and/or sorcery card in hand that can be cast using X or less colored mana, where X is equal to four plus twice the number of instants and sorceries you've cast this turn.
You have enough mana to cast the additional instant or sorcery, plus an additional.
Mana Needed
({U} magic symbol) if you have not cast an instant or sorcery this turn available.
Steps
Cast any other instant or sorcery spell by paying its mana cost.
Storm-Kiln Artist triggers, as well as
Thousand-Year Storm if you've cast another instant and/or sorcery spell this turn.
Resolve the
Storm-Kiln Artist trigger, creating a Treasure artifact token.
Resolve the
Thousand-Year Storm trigger, if applicable, copying the spell at least once.
Storm-Kiln Artist triggers for each copy made this way, creating that many Treasure artifact tokens.
Resolve each copy of the instant or sorcery.
Holding priority, activate two Treasures by tapping and sacrificing them, adding ({U} magic symbol) ({U} magic symbol) .
Cast
Narset's Reversal by paying ({U} magic symbol) ({U} magic symbol) , targeting the spell cast in step 1.
Thousand-Year Storm and
Storm-Kiln Artist trigger.
Resolve the
Storm-Kiln Artist trigger, creating a Treasure artifact token.
Resolve the
Thousand-Year Storm trigger, creating at least one copy of
Narset's Reversal, with each copy targeting the original
Narset's Reversal.
Storm-Kiln Artist triggers for each copy made this way, creating that many Treasure artifact tokens.
Resolve the first copy of
Narset's Reversal, copying
Narset's Reversal with the copy targeting the spell cast in step 1, and then returning the original
Narset's Reversal to your hand.
All remaining
Narset's Reversal copies made in step 11 fizzle due to having no legal target.
Storm-Kiln Artist triggers, creating a Treasure artifact token.
Resolve the
Narset's Reversal copy from step 13, copying the spell it is targeting and returning the original spell to your hand.
Storm-Kiln Artist triggers, creating a Treasure artifact token.
Resolve the copy of the spell.
Activate any number of Treasures by tapping and sacrificing them, adding enough mana to cast the additional instant or sorcery.
Repeat.
Once you have infinite mana, you may repeat this combo targeting any other instant and/or sorcery card in your hand and/or on the stack.
Results
Infinite colored mana.
Infinite copies of any instants and/or sorceries on the stack.