Blood of Purification

As an additional cost to cast Blood of Purification,
tap three target creatures you control.
At the beginning of your upkeep, tap three
creatures you control, then put a -1/-1 counter on
each of them. If you cant, exile Blood of Purification.
{3}{b}: Distribute two -1/-1 counters amongst
creatures target opponent controls for each -1/-1 counter on a creature you control.