Karn, Legacy Reforged 49/50 (March of the Machine: The Aftermath)

Karn's power and toughness are each equal to the greatest mana value among artifacts you control. At the beginning of your upkeep, add {C} for each artifact you control. This mana can't be spent to cast nonartifact spells. Until end of turn, you don't lose this mana as steps and phases end.

NM - $38.80
LP - $31.10
MP - $23.30
HP - $15.60
DMG - $7.80