Sacrifice Ebondeath with Ashnod's Altar to add two mana
Pitiless Plunderer's ability will trigger, create a Treasure token
Wilhelt's ability will trigger, create a Zombie token
Sacrifice the Zombie Token to add two more mana with Ashnod's Altar
Pitiless Plunderer's ability will create another Treasure token
Cast Ebondeath from your Graveyard by sacrificing the Treasures
Repeat the process for infinite mana.