Hydra's Growth is a uncommon Enchantment — Aura card from Theros Beyond Death (THB), collector number 172. Current market price: $1.70 (foil $1.95), TCGplayer market prices via Scryfall.
Enchant creature When this Aura enters, put a +1/+1 counter on enchanted creature. At the beginning of your upkeep, double the number of +1/+1 counters on enchanted creature.