Cast Persist by paying its mana cost, targeting any applicable target.
Holding priority, cast Dualcaster Mage by paying its mana cost.
When Dualcaster Mage enters, it triggers, targeting Persist.
Holding priority, activate Shilgengar by sacrificing Dualcaster Mage.
Resolve the Dualcaster Mage trigger, copying Persist, with the copy targeting Dualcaster Mage
Resolve the Persist copy, returning Dualcaster Mage from your graveyard to the battlefield.
Repeat from step 3.
This clever loop revolves around copying spells on the stack to recursively resurrect your creatures. You kick things off by casting Persist, then flash in Dualcaster Mage whose enters-the-battlefield ability targets the original Persist on the stack. Before that copy resolves, you sacrifice Dualcaster Mage to Shilgengar, Sire of Famine, which conveniently banks you a Blood token for your trouble. The resulting copy of Persist then drags Dualcaster Mage right back out of the graveyard, letting you repeat the whole sequence to generate boundless sacrifice triggers and an endless sea of Blood tokens.