Churning Reservoir is a uncommon Artifact card from Phyrexia: All Will Be One (ONE), collector number 127. Current market price: $0.24 (foil $0.10), TCGplayer market prices via Scryfall.
At the beginning of your upkeep, put an oil counter on another target nontoken artifact or creature you control. {2}, {T}: Create a 1/1 red Phyrexian Goblin creature token. Activate only if an oil counter was removed from a permanent you controlled this turn or a permanent with an oil counter on it was put into a graveyard this turn.