Vaal Hazak, Sinister Dragon

{b}{b}: Whenever a creature deals damage to or is dealt damage by Vaal Hazak this turn,
put two effluvia counters on it.
{b}: Put one effluvia counter on target creature.
{4}{b}: All creatures with four or more effluvia markers receive a -X/-X counter, where X is half of its power/toughness. Do this only once.