Doomhead Geist

Flying, Coalesce (When you cast this spell, you may
sacrifice any number of spirit you control. This spell
cost {1} less to cast for each spirit sacrificed this way.)
Doomhead Geist enter the battlefield with X
+1/+1 counters.
When Doomhead Geist dies Create X 1/1 black
Spirit creature tokens, where X is it's power.