Activate Whisper, Blood Liturgist, sacrificing itself and an additional creature to return Volrath's Shapeshifter from the graveyard to the battlefield.
Xathrid Necromancer triggers, creating a zombie token.
Volrath's Shapeshifter enters the battlefield as a copy of Whisper, Blood Liturgist.
Activate Volrath's Shapeshifter, sacrificing itself and a zombie token to return Whisper, Blood Liturgist to the battlefield.
Xathrid Necromancer triggers, creating a zombie token.