Leyline of Impending Darkness

If Leyline of Impending Darkness is in your opening hand, you may begin the game with it
on the battlefield.
Whenever a creature dies for the first time each turn, put a sacrifice counter on Leyline of Impending Darkness. Then, if there are four or more sacrifice counters on it, remove those
counters and create a 6/6 black Demon creature token with flying.