Thassa's Emissary is a uncommon Enchantment Creature — Crab card from The List (PLST), collector number THS-68. Current market price: $0.16, TCGplayer market prices via Scryfall.
Bestow {5}{U} (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 deals combat damage to a player, draw a card. Enchanted creature gets +3/+3.