Corpsehost Parasite

Afflict, Parasitic (Attach this creature to target creature as it enters the battlefield. If it is not attached to a creature, sacrifice it. The creature it's attached to is its host.)
Partner with Zombies (When this creature enters the battlefield, target player reveals a Zombie card from their library and put it into their hand, then shuffle.)
Some parasites feed off the living, some prefer to live off the feeding.