Requires

Invoke Calamity must be in hand. Narset's Reversal must be in hand, or in the graveyard. Thousand-Year Storm must be on the battlefield. You have cast at least one instant or sorcery spell this turn. Mana needed:

Steps

1. Cast Invoke Calamity by paying .
2. Thousand-Year Storm triggers, copying Invoke Calamity a number of times equal to the number of other instants and sorceries you have cast this turn.
3. Resolve all but two of the copies of Invoke Calamity and the original Invoke Calamity, choosing not to cast any instant or sorcery spells as they resolve.
4. Resolve a copy of Invoke Calamity, casting Narset's Reversal without paying its mana cost.
5. Thousand-Year Storm triggers, copying Narset's Reversal a number of times equal to the number of other instants and sorceries you have cast this turn, targeting the original Narset's Reversal with the first copy of Narset's Reversal and targeting the original Invoke Calamity with all other copies of Narset's Reversal.
6. Resolve a copy of Narset's Reversal, copying the original Invoke Calamity and returning it to your hand.
7. Resolve the newly copied Invoke Calamity, choosing not to cast any instant or sorcery spells as it resolves.
8. Each remaining copy of Narset's Reversal that was targeting the original Invoke Calamity fails to resolve due to no longer having a legal target.
9. Resolve the copy of Narset's Reversal targeting the original Narset's Reversal, copying it and returning it to your hand.
10. Resolve the newly copied Narset's Reversal, copying the remaining copy of Invoke Calamity and returning it to your hand.
11. Resolve the copied Invoke Calamity, casting Invoke Calamity without paying its mana cost.
12. Repeat from step 2 an arbitrarily large number of times.
13. Once you have done so, you may choose to cast any number of instants or sorceries from your hand or graveyard with mana value six or less without paying their mana costs during step 3.

Results