Primal Plasma is a common Creature — Elemental Shapeshifter card from Duel Decks: Venser vs. Koth (DDI), collector number 16. Current market price: $0.40, TCGplayer market prices via Scryfall.
As this creature enters, it becomes your choice of a 3/3 creature, a 2/2 creature with flying, or a 1/6 creature with defender.