Most played cards in URW composition:

1 Decks
Mishra's Factory
4 copies - 4 average
Serendib Efreet
4 copies - 4 average
Divine Offering
4 copies - 4 average
Disenchant
4 copies - 4 average
Black Vise
4 copies - 4 average
Chain Lightning
4 copies - 4 average
Lightning Bolt
4 copies - 4 average
Psionic Blast
4 copies - 4 average
Strip Mine
4 copies - 4 average
City of Brass
4 copies - 4 average
Savannah Lions
4 copies - 4 average
Plateau
3 copies - 3 average
Tundra
3 copies - 3 average
Volcanic Island
3 copies - 3 average
Spirit Link
3 copies - 3 average
Control Magic
2 copies - 2 average
Atog
2 copies - 2 average
Falling Star
1 copies - 1 average
Balance
1 copies - 1 average
Library of Alexandria
1 copies - 1 average