Most played cards in Ruhan of the Fomori:

4 Decks
Scalding Tarn
4 copies - 1 average
Steam Vents
4 copies - 1 average
Polluted Delta
4 copies - 1 average
Tundra
4 copies - 1 average
Brainstorm
4 copies - 1 average
Windswept Heath
4 copies - 1 average
Fact or Fiction
4 copies - 1 average
Council's Judgment
4 copies - 1 average
Force of Will
4 copies - 1 average
Lightning Bolt
4 copies - 1 average
Jace, the Mind Sculptor
4 copies - 1 average
Arid Mesa
4 copies - 1 average
Plateau
4 copies - 1 average
Sacred Foundry
4 copies - 1 average
Misty Rainforest
4 copies - 1 average
Flooded Strand
4 copies - 1 average
Command Tower
4 copies - 1 average
Marsh Flats
4 copies - 1 average
Bloodstained Mire
4 copies - 1 average
Swords to Plowshares
4 copies - 1 average