Ruin Crab is a rare Creature — Crab card from Secret Lair Drop (SLD), collector number 7095. Current market price: $5.03 (foil $4.71), TCGplayer market prices via Scryfall.
Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)