Peryite, Lord of Plagues

Whenever a creature dies, if it had a -1/-1
counter on it, put a +1/+1 counter on
Peryite. At the beginning of your upkeep,
you may pay X life, where X is the number
of +1/+1 counters on Peryite. If you do,
each opponent loses X life and you gain X
life.