Bloody Benten

This spell costs {1} less to cast for each creature
in your graveyard.
{w/b}{w/b}{w/b}, {t}: Target player loses 1 life for each
creature in all graveyards.
At the beginning of your endstep, reveal the top
card of your library, if its mana value is greater
than four, put it into your hand and gain 4 life.