Treacherous Vampire

Flying Whenever this creature attacks or blocks, sacrifice it unless you exile a card from your graveyard. Threshold — As long as there are seven or more cards in your graveyard, this creature gets +2/+2 and has "When this creature dies, you lose 6 life."

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6oichhd7z1pb1hom63oa74.