Training of the Returned

{2}{b}{b}, {t}: Create a 2/2 black Zombie creature
token with disease 1. (When this creature enters the battlefield, put a disease counter on target creature.)
{3}{b}{b}, {t}: Create X 2/2 black Zombie creature tokens, where X is the number of Zombies you control. Activate this ability only if there are
three or more creatures with disease counters on
the battlefield.