Liber Sanguinis

{p/b}, Put a -1/-1 counter on a creature you control:
Put a page counter on Liber Sanguinis. Surveil 2. Activate only as a sorcery.
{t}, Remove X page counters from Liber
Sanguinis: Search your graveyard and/or library
for a Demon card with mana value X or less and
put it onto the battlefield. If you search your
library this way, shuffle.
Pages of flayed flesh, inked in blood.