When Bloodtithe Harvester enters the battlefield, create a
Blood token
(A Blood token is an artifact with ", , Discard a card, Sacrifice this artifact: Draw a card.").
, Sacrifice Bloodtithe Harvester: Target creature gets -X/-X until end of turn, where X is twice the number of
Blood tokens
(A Blood token is an artifact with ", , Discard a card, Sacrifice this artifact: Draw a card.") you control. Activate only as a sorcery.