Gridon, Demon of the Edge

When Gridon, Demon of the Edge enters the battlefield, destroy x amount of permanents
an opponent controls, where x is the amount
of creatures in your graveyard.
{t}{r}: create a 3/3 demon.
{b}: Gridon, Demon of the Edge gains +1/+1.
{t}{r}{r}{b}{b}: exile a graveyard.