Most played cards in Mono Red Prison:

1 Decks
Chalice of the Void
4 copies - 4 average
Blood Moon
4 copies - 4 average
Ancient Tomb
4 copies - 4 average
Chrome Mox
4 copies - 4 average
Shatterskull Smashing
4 copies - 4 average
Leyline of the Void
4 copies - 4 average
Trinisphere
4 copies - 4 average
Legion Warboss
4 copies - 4 average
Fable of the Mirror-Breaker
4 copies - 4 average
Simian Spirit Guide
4 copies - 4 average
Fury
4 copies - 4 average
Goblin Rabblemaster
4 copies - 4 average
City of Traitors
4 copies - 4 average
Magus of the Moon
3 copies - 3 average
Bonecrusher Giant
3 copies - 3 average
Fiery Confluence
2 copies - 2 average
Fireflux Squad
2 copies - 2 average
Dead // Gone
2 copies - 2 average
Pyroblast
2 copies - 2 average
Den of the Bugbear
1 copies - 1 average