Ghalta, Primal Hunger is a rare Legendary Creature — Elder Dinosaur card from Rivals of Ixalan (RIX), collector number 130. Current market price: $1.40 (foil $4.23), TCGplayer market prices via Scryfall.
This spell costs {X} less to cast, where X is the total power of creatures you control. Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)