Morbid Mentor

Whenever a creature dies put a counter on
Morbid Mentor.
If Morbid Mentor has 3 or more counters, you
may remove 3 counter and pay {b/g}{b/g}: Exile a
creature from a graveyard, put a +1/+1 counter
on a creature you control or put -1/-1 counter on
a creature you don't control.
Take notes so you don't forget, life and death are beautifully complementary.