Requires

Invoke Calamity must be in hand. Narset's Reversal must be in hand, or in the graveyard. Swarm Intelligence must be on the battlefield. Mana needed:

Steps

1. Cast Invoke Calamity by paying .
2. Swarm Intelligence triggers, copying Invoke Calamity.
3. Resolve the Invoke Calamity copy, casting Narset's Reversal without paying its mana cost.
4. Swarm Intelligence triggers, copying Narset's Reversal targeting the original Narset's Reversal.
5. Resolve the copy of Narset's Reversal, copying Narset's Reversal targeting Invoke Calamity and returning the original Narset's Reversal to your hand.
6. Resolve the Narset's Reversal copy, copying Invoke Calamity and returning the original Invoke Calamity to your hand.
7. Resolve the Invoke Calamity copy, casting Invoke Calamity without paying its mana cost.
8. Repeat from step 2.
9. You may also choose to cast any number of instants or sorceries from your hand or graveyard with mana value 4 or less without paying their mana costs during step 3.

Results