Heliod's Emissary is a uncommon Enchantment Creature — Elk card from Theros (THS), collector number 18. Current market price: $0.18 (foil $0.42), TCGplayer market prices via Scryfall.
Bestow {6}{W} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.) Whenever this creature or enchanted creature attacks, tap target creature an opponent controls. Enchanted creature gets +3/+3.