Dragon Roost

Dragon Roost enters the battlefield with three slumber counters on it. At the beginning of your upkeep, remove a slumber counter from Dragon Roost. When the last counter is removed, sacrifice this card and create a 5/6 red Dragon creature named Inviolus Vox with "Whenever a creature dealt damage by Inviolus Vox dies this turn, put a +1/+1 counter on this card, then summon a copy of me. This ability triggers only once each turn."