Ruin Crab is a uncommon Creature — Crab card from Zendikar Rising (ZNR), collector number 295. Current market price: $1.20 (foil $1.61), 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.)