Sheoldred, Whispering One is a mythic Legendary Creature — Phyrexian Praetor card from Iconic Masters (IMA), collector number 108. Current market price: $22.69 (foil $36.18), 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.