Vulat, Grave Watcher

Indestructible
Vulat's power and toughness are each equal
to the number of permanent cards in your opponents' graveyards.
{w/b}{w/b}: The next instant or sorcery spell you cast this turn has gravestorm. (When you cast the spell, copy it for each permanent put into a graveyard this turn. You may choose new targets for the copies.)