Summoning Circle

{1}, Sacrifice a Creature: Put a number of rite
counters on Summoning Circle equal to the sacrificed creature's mana value. You gain 1 life.
At the beginning of your upkeep, if Summoning
Circle has eight or more rite counters on it, you
may sacrifice it. If you do, search your library for
a Demon creature card, put it onto the
battlefield, then shuffle.