Yiazmat, Final Hour

Flying, Trample, Ward {4}

When Yiazmat enters the battlefield, create a legendary colorless artifact token named Ashen Hourglass with indestructible and "Ashen Hourglass enters the battlefield with 50 time counters on it.
At the beginning of each upkeep, remove a time counter from Ashen Hourglass.
Then, if it has no time counters on it, each opponent loses the game.
Whenever a creature dies, remove a time counter from Ashen Hourglass."