Journal of the Ancient Void

Journal of the Ancient Void enters with X void counters on it.
Whenever you play a black spell, you may remove a void counter from Journal of the Ancient Void. If you do, each opponent sacrifices a creature. Then if there are no more void counters on it, sacrifice a creature. Then, create a legendary 4/4 black demon creature token with flying and deathtouch named Gidask.