Nekroz, the Death Bringer

Other Zombies you control have menace as long as its
your turn. Otherwise, they gain deathtouch.
Whenever a creature dies in an opponent's turn, amass zombies 1. (Put one +1/+1 counters on an Army you
control. It's also a Zombie. Of you don't control an
Army, create a 0/0 black Zombie Army creature token
first.)