Vesperlark | Body Double | Shilgengar, Sire of Famine

Cards

Vesperlark in your graveyard.
Body Double and
Shilgengar on the battlefield (
Body Double as a copy of
Vesperlark).

Activate
Shilgengar by sacrificing
Body Double.
When
Body Double leaves the battlefield, its
Vesperlark ability triggers, returning itself from your graveyard to the battlefield as a copy of
Vesperlark.
Resolve the
Shilgengar ability.
Repeat.

This combo has been estimated to be Exhibition (Bracket 1+).