Amassing Dead

Zombies you control get +1/+1 and have haste.
At the beginning of your upkeep, you may
sacrifice a nontoken creature, if you do, create X
2/2 black Zombie creature tokens where X is
equal to half the sacrificed creatures converted
mana cost, rounded up.
At the beginning of your endstep, if you control
twenty or more zombies, you win the game.
From the bodies on the dead came forth innumerable
forms and they tore through the armies or man.