Kritav, Master Corpsecrafter

Whenever another Zombie or Skeleton enters the
battlefield under your control, put two +1/+1
counters on it.
{x}, {t}: Return up to two target creature cards
with total mana value X or less from a graveyard
to the battlefield under your control, those
creatures are Zombies in addition to their other
types. Activate only as a sorcery.