Nurgle, Lord of Decay

This spell costs {x} less to cast where X is the
number of -1/-1 counters on creatures your
opponents control.
Ward—Put a -1/-1 counter on each creature you control.
Whenever a nontoken creature dies, note the
number of -1/-1 counters on it and choose one
where X is the noted number:
•Each opponent loses X life and you gain X life
•Create X 1/1 green Nurgling Demon
tokens