Cast Sevinne's Reclamation 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 Sevinne's Reclamation.
Holding priority, activate Shilgengar by sacrificing Dualcaster Mage.
Resolve the Dualcaster Mage trigger, copying Sevinne's Reclamation, with the copy targeting Dualcaster Mage
Resolve the Sevinne's Reclamation copy, returning Dualcaster Mage from your graveyard to the battlefield.
Repeat from step 3.
This elegant loop is orchestrated by Shilgengar, Sire of Famine, whose sacrificial engine turns your creatures into currency while holding the ultimate promise of mass resurrection. By casting Sevinne's Reclamation and slipping in a flash-cast Dualcaster Mage to copy it on the stack, you create a recursive heartbeat: Dualcaster Mage targets the original spell, enters to copy it, and then feeds itself to Shilgengar, Sire of Famine just in time to be brought right back by the copy. The blood tokens left behind by Shilgengar, Sire of Famine accumulate boundlessly with every iteration, setting the stage for you to eventually cash them in and return your entire graveyard to the battlefield.