Demon Blood Ritual

Cumulative upkeep—Pay 1 life. (At the beginning
of your upkeep, put an age counter on this permanent,
then sacrifice it unless you pay its upkeep cost for each
age counter on it.)
Demon creature spells you cast have Bloodthirst
X, where X is the number of age counters on
Demon Blood Ritual. (If an opponent was dealt
damage this turn, this creature enters the battlefield
with X +1/+1 counter on it.)