Sarinth Greatwurm is a mythic Creature — Wurm card from The Brothers' War Promos (PBRO), collector number 220s. Current market price: — (foil $2.08), 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.")