Activate Shilgengar by sacrificing another creature.
When the creature dies, its persist ability triggers, returning it from your graveyard to the battlefield without a -1/-1 counter on it due to Vizier of Remedies.
Resolve the Shilgengar ability.
Repeat.
This loop hinges on a clever interaction between undeath and mitigation: Eirdu, Carrier of Dawn provides your nontoken creatures with persist, which normally brings them back with a -1/-1 counter, but Vizier of Remedies steps in to reduce that counter placement to zero. With the counter prevention safely in place, Shilgengar, Sire of Famine can repeatedly sacrifice your creatures to churn out a mountain of Blood tokens. Once you have a sufficient pile, Shilgengar's own mass-reanimation ability can be fueled to bring everything back, transforming your board into an unstoppable engine of sacrifice.