Activate Shilgengar by sacrificing Reassembling Skeleton.
When Reassembling Skeleton dies, Pitiless Plunderer and Bridge from Below 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 Reassembling Skeleton by paying 1, returning it from your graveyard to the battlefield.
Repeat.
This clever loop relies on Shilgengar, Sire of Famine to repeatedly consume your own forces, turning each sacrifice into a steady stream of Blood tokens. To keep the engine running, Reassembling Skeleton acts as a tireless, recurring sacrifice fodder that brings itself back from the graveyard using the mana generated by Pitiless Plunderer whenever a creature dies. Meanwhile, Bridge from Below quietly sits in your graveyard to pump out extra Zombie tokens off those same creature deaths, padding your sacrifice resources even further without draining your mana supply.