Ashaya, Soul of the Wild is a mythic Legendary Creature — Elemental card from Secret Lair Drop (SLD), collector number 2014. Current market price: $31.62, TCGplayer market prices via Scryfall.
Ashaya's power and toughness are each equal to the number of lands you control. Nontoken creatures you control are Forest lands in addition to their other types. (They're still affected by summoning sickness.)