Lifelink
If a nontoken creature an opponent controls would die, instead exile that card and create a 2/2 black Zombie creature token.
{2}{B}, Sacrifice another Vampire or Zombie: Put two +1/+1 counters on Kalitas, Traitor of Ghet.
Abilities that trigger whenever a creature an opponent controls dies won’t trigger unless that creature is a token (see below).
If Kalitas dies at the same time as creatures your opponents control, those creature cards will be exiled and you’ll get that many Zombies.
If a creature token an opponent controls dies, it goes to that player’s graveyard as normal before ceasing to exist.
You can’t sacrifice Kalitas to activate the last ability, even if it’s somehow become a Zombie.