Aboleth Spawn

Flash
Ward {2}
Probing Telepathy — Whenever a creature entering under an opponent's control causes a triggered ability of that creature to trigger, you may copy that ability. You may choose new targets for the copy.

Haunted One

Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying 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.)

Sludge Monster

Whenever Sludge Monster enters or attacks, put a slime counter on up to one other target creature.
Non-Horror creatures with slime counters on them lose all abilities and have base power and toughness 2/2.

Devour Intellect

Target opponent discards a card. If mana from a Treasure was spent to cast this spell, instead that player reveals their hand, you choose a nonland card from it, then that player discards that card.

Extract from Darkness

Each player mills two cards. Then you put a creature card from a graveyard onto the battlefield under your control.

In Garruk's Wake

Destroy all creatures you don't control and all planeswalkers you don't control.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Hunted Horror

Trample
When Hunted Horror enters, target opponent creates two 3/3 green Centaur creature tokens with protection from black.

Curtains' Call

Undaunted (This spell costs {1} less to cast for each opponent.)
Destroy two target creatures.

Sol Ring

Spellskite

{U/P}: Change a target of target spell or ability to Spellskite. ({U/P} can be paid with either {U} or 2 life.)

Memory Plunder

You may cast target instant or sorcery card from an opponent's graveyard without paying its mana cost.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Nighthowler

Bestow {2}{B}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Nighthowler and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards.

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Endless Evil

Enchant creature you control
At the beginning of your upkeep, create a token that's a copy of enchanted creature, except the token is 1/1.
When enchanted creature dies, if that creature was a Horror, return Endless Evil to its owner's hand.

Dross Harvester

Protection from white
At the beginning of your end step, you lose 4 life.
Whenever a creature dies, you gain 2 life.

Dusk Mangler

As an additional cost to cast this spell, sacrifice a creature, discard a card, or pay 4 life.
When Dusk Mangler enters, each opponent sacrifices a creature, discards a card, and loses 4 life.

Haunted Cloak

Equipped creature has vigilance, trample, and haste.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Syphon Mind

Each other player discards a card. You draw a card for each card discarded this way.

Cloud Key

As Cloud Key enters, choose artifact, creature, enchantment, instant, or sorcery.
Spells you cast of the chosen type cost {1} less to cast.

Port of Karfell

Port of Karfell enters tapped.
{T}: Add {U}.
{3}{U}{B}{B}, {T}, Sacrifice Port of Karfell: Mill four cards, then return a creature card from your graveyard to the battlefield tapped. (To mill a card, put the top card of your library into your graveyard.)

Woe Strider

When Woe Strider enters, create a 0/1 white Goat creature token.
Sacrifice another creature: Scry 1.
Escape—{3}{B}{B}, Exile four other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)
Woe Strider escapes with two +1/+1 counters on it.

River of Tears

{T}: Add {U}. If you played a land this turn, add {B} instead.

Guiltfeeder

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever Guiltfeeder attacks and isn't blocked, defending player loses 1 life for each card in their graveyard.

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Defiler of Flesh

Menace
As an additional cost to cast black permanent spells, you may pay 2 life. Those spells cost {B} less to cast if you paid life this way. This effect reduces only the amount of black mana you pay.
Whenever you cast a black permanent spell, target creature you control gets +1/+1 and gains menace until end of turn.

Phyrexian Rager

When Phyrexian Rager enters, you draw a card and you lose 1 life.

Dimir Signet

Spoils of Blood

Create an X/X black Horror creature token, where X is the number of creatures that died this turn.

Dimir Keyrune

{T}: Add {U} or {B}.
{U}{B}: Dimir Keyrune becomes a 2/2 blue and black Horror artifact creature until end of turn and can't be blocked this turn.

Ravenous Chupacabra

When Ravenous Chupacabra enters, destroy target creature an opponent controls.

Nemesis of Reason

Whenever Nemesis of Reason attacks, defending player mills ten cards.

Brainstealer Dragon

Flying
At the beginning of your end step, exile the top card of each opponent's library. You may play those cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.
Whenever a nonland permanent an opponent owns enters the battlefield under your control, they lose life equal to its mana value.

Wharf Infiltrator

Skulk (This creature can't be blocked by creatures with greater power.)
Whenever Wharf Infiltrator deals combat damage to a player, you may draw a card. If you do, discard a card.
Whenever you discard a creature card, you may pay {2}. If you do, create a 3/2 colorless Eldrazi Horror creature token.

Blistergrub

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
When Blistergrub dies, each opponent loses 2 life.

Dark Hatchling

Flying
When Dark Hatchling enters, destroy target nonblack creature. It can't be regenerated.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Mind Flayer

Dominate Monster — When Mind Flayer enters, gain control of target creature for as long as you control Mind Flayer.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)

Phyrexian Revoker

As Phyrexian Revoker enters, choose a nonland card name.
Activated abilities of sources with the chosen name can't be activated.

Swamp

Island

Overcharged Amalgam

Flash
Flying
Exploit (When this creature enters, you may sacrifice a creature.)
When Overcharged Amalgam exploits a creature, counter target spell, activated ability, or triggered ability.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Nephalia Drownyard

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

Chasm Skulker

Whenever you draw a card, put a +1/+1 counter on Chasm Skulker.
When Chasm Skulker dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on Chasm Skulker. (They can't be blocked as long as defending player controls an Island.)

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

Darkwater Catacombs

Command Tower

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. Talisman of Dominance deals 1 damage to you.

Psionic Ritual

Replicate—Tap an untapped Horror you control. (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Exile target instant or sorcery card from a graveyard and copy it. You may cast the copy without paying its mana cost.
Exile Psionic Ritual.

Crippling Fear

Choose a creature type. Creatures that aren't of the chosen type get -3/-3 until end of turn.

Captain N'ghathrod

Horrors you control have menace.
Whenever a Horror you control deals combat damage to a player, that player mills that many cards.
At the beginning of your end step, choose target artifact or creature card in an opponent's graveyard that was put there from their library this turn. Put it onto the battlefield under your control.

Grazilaxx, Illithid Scholar

Whenever a creature you control becomes blocked, you may return it to its owner's hand.
Whenever one or more creatures you control deal combat damage to a player, draw a card.

Rogue's Passage

{T}: Add {C}.
{4}, {T}: Target creature can't be blocked this turn.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Gurgling Anointer

Flying
Whenever you draw your second card each turn, put a +1/+1 counter on Gurgling Anointer.
When Gurgling Anointer dies, return another target creature card with mana value less than or equal to Gurgling Anointer's power from your graveyard to the battlefield.

Carrion Locust

Flying
When Carrion Locust enters, exile target card from an opponent's graveyard. If it was a creature card, that player loses 1 life.

Forgotten Creation

Skulk (This creature can't be blocked by creatures with greater power.)
At the beginning of your upkeep, you may discard all the cards in your hand. If you do, draw that many cards.

Uchuulon

Uchuulon's power is equal to the number of Crabs, Oozes, and/or Horrors you control.
Horrific Symbiosis — At the beginning of your end step, exile up to one target creature card from an opponent's graveyard. If you do, create a token that's a copy of Uchuulon.

Choked Estuary

As Choked Estuary enters, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters tapped.
{T}: Add {U} or {B}.

Changeling Outcast

Changeling (This card is every creature type.)
Changeling Outcast can't block and can't be blocked.

Sewer Nemesis

As Sewer Nemesis enters, choose a player.
Sewer Nemesis's power and toughness are each equal to the number of cards in the chosen player's graveyard.
Whenever the chosen player casts a spell, that player mills a card.

Chariot of Victory

Equipped creature has first strike, trample, and haste.
Equip {1}

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Dauthi Horror

Shadow (This creature can block or be blocked by only creatures with shadow.)
Dauthi Horror can't be blocked by white creatures.

Grell Philosopher

Aberrant Tinkering — When Grell Philosopher enters and at the beginning of your upkeep, each Horror you control gains all activated abilities of target artifact an opponent controls until end of turn. You may spend blue mana as though it were mana of any color to activate those abilities.

From the Catacombs

Put target creature card from a graveyard onto the battlefield under your control with a corpse counter on it. You take the initiative. If that creature would leave the battlefield, exile it instead of putting it anywhere else.
Escape—{3}{B}{B}, Exile five other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Consuming Aberration

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Nihilith

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Suspend 7—{1}{B} (Rather than cast this card from your hand, you may pay {1}{B} and exile it with seven time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)
Whenever a card is put into an opponent's graveyard from anywhere, if Nihilith is suspended, you may remove a time counter from Nihilith.

Drown in the Loch

Choose one —
• Counter target spell with mana value less than or equal to the number of cards in its controller's graveyard.
• Destroy target creature with mana value less than or equal to the number of cards in its controller's graveyard.

Fractured Sanity

Each opponent mills fourteen cards.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle Fractured Sanity, each opponent mills four cards.

Reflections of Littjara

As Reflections of Littjara enters, choose a creature type.
Whenever you cast a spell of the chosen type, copy that spell. (A copy of a permanent spell becomes a token.)