Most played cards in Narset Undoing:

3 Decks
Narset, Parter of Veils
12 copies - 4 average
Serum Visions
10 copies - 3.33 average
Opt
9 copies - 3 average
Remand
8 copies - 2.67 average
Snapcaster Mage
8 copies - 2.67 average
Thing in the Ice
7 copies - 2.33 average
Flooded Strand
7 copies - 2.33 average
Day's Undoing
7 copies - 2.33 average
Snow-Covered Island
6 copies - 2 average
Cryptic Command
5 copies - 1.67 average
Force of Negation
5 copies - 1.67 average
Leyline of the Void
4 copies - 1.33 average
Rest in Peace
4 copies - 1.33 average
Scalding Tarn
4 copies - 1.33 average
Field of Ruin
4 copies - 1.33 average
Lightning Bolt
4 copies - 1.33 average
Path to Exile
4 copies - 1.33 average
Spell Pierce
4 copies - 1.33 average
Jace, the Mind Sculptor
3 copies - 1 average
Vendilion Clique
3 copies - 1 average