Sarinth Greatwurm is a mythic Creature — Wurm card from The Brothers' War (BRO), collector number 220. Current market price: $0.66 (foil $0.49), TCGplayer market prices via Scryfall.
Trample Whenever a land enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")