Sultai Emissary is a common Creature — Zombie Warrior card from Ugin's Fate (UGIN), collector number 85. Current market price: $1.00, TCGplayer market prices via Scryfall.
When this creature dies, manifest the top card of your library. (Put that card onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)