Blood Divination

The math is the problem. Four mana plus a creature to draw three cards flat the moment you set it against the black card-draw it shares a lineage with: Sign in Blood and Night's Whisper buy two cards for two mana off your own life, and Read the Bones throws in scry. Asking for both a higher mana value and a body on the battlefield, then feeding that body to refill, is a worse trade in any deck that only wants cards. What the sacrifice clause is reaching for is the aristocrats wrinkle: a creature you sacrifice is not a creature you discard. If that body carries a death trigger, an undying or persist counter, a graveyard payoff, or a recursion plan, the additional cost stops reading as pure tax and starts doubling as enabler. That is the only frame in which the line looks designed rather than overpriced: it wants you to spend something that wanted to die anyway, so the three cards become the second half of a two-for-one you were already going to trigger. Strip that context away and it is a draw spell that asks too much and returns too little, black card-advantage filler that exists to give sacrifice-matters builds another payoff to point their engine at, not to win a game on its own.