Nezarec, Final God of Pain

Whenever a creature you don't control dies, place
a 1/1 Nightmare with flying onto the battlefield
under your control. Then, if you control 10 or
more Nightmare creatures, Nezarec deals 10
damage to all creatures.
Whenever a Nightmare dies, put a +1/+1
counter onto Nezarec.
"Your minds are mine to torment." -Nezarec