Molten Man, Inferno Incarnate is a uncommon Legendary Creature — Elemental Villain card from Marvel's Spider-Man (SPM), collector number 84. Current market price: $0.21 (foil $0.29), TCGplayer market prices via Scryfall.
When Molten Man enters, search your library for a basic Mountain card, put it onto the battlefield tapped, then shuffle. Molten Man gets +1/+1 for each Mountain you control. When Molten Man leaves the battlefield, sacrifice a land.