Vuinuhr, Overlord of Death

When Vuinuhr, Overlord of Darkness enters the battlefield, put X 1/1 black demon tokens onto the battlefield, where X is his converted mana cost -3.
At the beginning of your upkeep, remove all +1/+1 counters from Vuinuhr, Overlord of Darkness, then put X +1/+1 counters on him, where X is the number of demons you control.
Other demons you control have +1/+1.
First Strike
Bring me their heads, my children!