Sheoldred, Whispering One
Legendary Creature - Phyrexian Praetor | Power/Toughness: 6 / 6 (CMC 7)
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.