Karn's Bastion is a rare Land card from Ravnica Remastered (RVR), collector number 464. Current market price: $4.39 (foil $5.25), TCGplayer market prices via Scryfall.
{T}: Add {C}. {4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)