Holding priority, cast Naru Meha by paying its mana cost.
When Naru Meha enters, it triggers, copying Presumed Dead, with the copy targeting Naru Meha.
Resolve the copy of Presumed Dead.
Holding priority, activate Shilgengar by sacrificing Naru Meha.
When Naru Meha dies, it triggers, returning it from your graveyard to the battlefield.
Repeat from step 3.
Resolve all Shilgengar abilities from step 5.
By casting Presumed Dead and responding with Naru Meha, Master Wizard, you set up an endlessly self-sustaining loop where Naru Meha targets herself with the copied spell's protection. With that recursive safety net in place, you can continually sacrifice Naru Meha to Shilgengar, Sire of Famine's activation cost. Every time she hits the graveyard, Presumed Dead's delayed trigger pulls her right back to the battlefield, where Naru Meha enters anew to copy the spell all over again while Shilgengar conveniently churns out an endless supply of Blood tokens.