Nyx Herald is a uncommon Enchantment Creature — Centaur Shaman card from Theros Beyond Death (THB), collector number 189. Current market price: $0.15 (foil $0.30), TCGplayer market prices via Scryfall.
At the beginning of combat on your turn, target enchanted creature or enchantment creature you control gets +1/+1 and gains trample until end of turn.