Activate Shilgengar by sacrificing Bloodsoaked Champion.
When Bloodsoaked Champion dies, Pitiless Plunderer and Rat King trigger, creating a creature token and a Treasure token.
Resolve the Shilgengar ability.
Activate Shilgengar by sacrificing the creature token.
When the creature token dies, Pitiless Plunderer triggers, creating a Treasure token.
Resolve the Shilgengar ability.
Activate the Treasures by tapping and sacrificing them, adding 1.
Activate Bloodsoaked Champion by paying 1, returning it from your graveyard to the battlefield.
Repeat.
This macabre loop relies on Shilgengar, Sire of Famine to sacrifice Bloodsoaked Champion, turning our valiant warrior into a steady stream of Blood tokens while fueling Pitiless Plunderer and Rat King, Pale Piper to generate a cascade of Treasures and Rat tokens whenever things perish. As those tokens feed further sacrifices back into Shilgengar, Sire of Famine, Pitiless Plunderer's Treasures provide the exact black mana needed to pay Bloodsoaked Champion's raid cost, allowing it to march endlessly out of the graveyard. Meanwhile, Rat King, Pale Piper turns every departure into more fodder and potential card draw, letting you overwhelm the board with endless artifact and creature triggers.