Thought Collapse

Counter target spell. Its controller mills three cards.

Diabolic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Unholy Grotto

{T}: Add {C}.
{B}, {T}: Put target Zombie card from your graveyard on top of your library.

Swamp

Nephalia Drownyard

{T}: Add {C}.
{1}{U}{B}, {T}: Target player mills three cards.

Gravecrawler

Gravecrawler can't block.
You may cast Gravecrawler from your graveyard as long as you control a Zombie.

Geralf's Mindcrusher

When Geralf's Mindcrusher enters, target player mills five cards.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Dimir Aqueduct

Dimir Aqueduct enters tapped.
When Dimir Aqueduct enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

Diregraf Captain

Deathtouch
Other Zombie creatures you control get +1/+1.
Whenever another Zombie you control dies, target opponent loses 1 life.

Trepanation Blade

Whenever equipped creature attacks, defending player reveals cards from the top of their library until they reveal a land card. The creature gets +1/+0 until end of turn for each card revealed this way. That player puts the revealed cards into their graveyard.
Equip {2}

Unbreathing Horde

Unbreathing Horde enters 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.

Undead Alchemist

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.

Maddening Cacophony

Kicker {3}{U}
Each opponent mills eight cards. If this spell was kicked, instead each opponent mills half their library, rounded up.

Endless Ranks of the Dead

At the beginning of your upkeep, create X 2/2 black Zombie creature tokens, where X is half the number of Zombies you control, rounded down.

Ghoulcaller Gisa

{B}, {T}, Sacrifice another creature: Create X 2/2 black Zombie creature tokens, where X is the sacrificed creature's power.

Champion of the Perished

Whenever another Zombie you control enters, put a +1/+1 counter on Champion of the Perished.

Diabolic Intent

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a card, put that card into your hand, then shuffle.

Drowned Catacomb

Drowned Catacomb enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Liliana's Mastery

Zombies you control get +1/+1.
When Liliana's Mastery enters, create two 2/2 black Zombie creature tokens.