Most played cards in Narset Undoing:

2 Decks
Narset, Parter of Veils
8 copies - 4 average
Serum Visions
7 copies - 3.5 average
Snow-Covered Island
6 copies - 3 average
Opt
5 copies - 2.5 average
Remand
4 copies - 2 average
Spell Pierce
4 copies - 2 average
Rest in Peace
4 copies - 2 average
Leyline of the Void
4 copies - 2 average
Flooded Strand
4 copies - 2 average
Field of Ruin
4 copies - 2 average
Path to Exile
4 copies - 2 average
Snapcaster Mage
4 copies - 2 average
Day's Undoing
4 copies - 2 average
Thing in the Ice
4 copies - 2 average
Cryptic Command
4 copies - 2 average
Jace, the Mind Sculptor
3 copies - 1.5 average
Commandeer
3 copies - 1.5 average
Vendilion Clique
3 copies - 1.5 average
Teferi, Time Raveler
2 copies - 1 average
Hallowed Fountain
2 copies - 1 average