Nylea's Disciple is a common Creature — Centaur Archer card from Theros (THS), collector number 167. Current market price: $0.10 (foil $0.51), TCGplayer market prices via Scryfall.
When this creature enters, you gain life equal to your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)