Unbreathing Horde enters the battlefield with a +1/+1 counter on it for each other Zombie you control and each Zombie card in your graveyard. If Unbreathing Horde would be dealt damage, prevent that damage and remove a +1/+1 counter from it.
If a Zombie you control would deal combat damage to a player, instead that player mills that many cards. Whenever a creature card is put into an opponent's graveyard from their library, exile that card and create a 2/2 black Zombie creature token.
"To show geists pity is to prolong their agonies. Whether they know it or not, they seek the Blessed Sleep, and we are to give it to them." —Mikaeus, the Lunarch
Play with the top card of your library revealed. As long as the top card of your library is black, Vampire Nocturnus and other Vampire creatures you control get +2/+1 and have flying.
"A long and difficult incision revealed that all vital organs are housed in the head, save for a long chain of stomachs, forty in all, leading from its throat to the end of the tail." —Mulak Ffar, Vastwood Biodiversity