Sheoldred, Whispering One is a mythic Legendary Creature — Phyrexian Praetor card from New Phyrexia (NPH), collector number 73. Current market price: $21.30 (foil $70.44), TCGplayer market prices via Scryfall.
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.) At the beginning of your upkeep, return target creature card from your graveyard to the battlefield. At the beginning of each opponent's upkeep, that player sacrifices a creature of their choice.