Pollywog Symbiote is a uncommon Creature — Frog card from Ikoria: Lair of Behemoths (IKO), collector number 372. Current market price: $2.34 (foil $2.94), TCGplayer market prices via Scryfall.
Each creature spell you cast costs {1} less to cast if it has mutate. Whenever you cast a creature spell, if it has mutate, draw a card, then discard a card.