Sedris, the Traitor King is a mythic Legendary Creature — Zombie Warrior card from Magic Online Promos (PRM), collector number 102323.
Each creature card in your graveyard has unearth {2}{B}. ({2}{B}: Return the card to the battlefield. The creature gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)