You may have Spark Double enter the battlefield as a copy of a creature or planeswalker you control, except it enters with an additional +1/+1 counter on it if it's a creature, it enters with an additional loyalty counter on it if it's a planeswalker, and it isn't legendary.

Draw two cards. Then discard a card unless you attacked this turn.

Whenever a creature you control deals combat damage to an opponent, you may draw a card.

Enchant creature Whenever enchanted creature deals damage to an opponent, you may draw a card.

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.

At the beginning of your upkeep, you draw a card and you lose 1 life.

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

Target player mills two cards. Draw two cards.

Whenever a creature you control deals combat damage to a player, you may draw a card. Cycling {2} ({2}, Discard this card: Draw a card.)

Draw a card. Scry 2.

Target player draws two cards and loses 2 life.

Target player mills two cards. Draw a card.

Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

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.)

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

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

Islandwalk (This creature can't be blocked as long as defending player controls an Island.) Water Always Wins — Whenever The Flood of Mars attacks, put a flood counter on another target creature or land. If it's a creature, it becomes a copy of The Flood of Mars. If it's a land, it becomes an Island in addition to its other types.

Flash Ward {2} Probing Telepathy — Whenever a creature entering the battlefield 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.

Aberrant Tinkering — When Grell Philosopher enters the battlefield 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.

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

When Mintstrosity dies, create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

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.

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

{T}: Add {C}. Basic landcycling {1} ({1}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

As Cavern of Souls enters the battlefield, choose a creature type. {T}: Add {C}. {T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

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

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

Dismal Backwater enters the battlefield tapped. When Dismal Backwater enters the battlefield, you gain 1 life. {T}: Add {U} or {B}.

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

You may have Echoing Deeps enter the battlefield tapped as a copy of any land card in a graveyard, except it's a Cave in addition to its other types. {T}: Add {C}.

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

({T}: Add {U}.)

Jwar Isle Refuge enters the battlefield tapped. When Jwar Isle Refuge enters the battlefield, you gain 1 life. {T}: Add {U} or {B}.

Morphic Pool enters the battlefield tapped unless you have two or more opponents. {T}: Add {U} or {B}.

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

Path of Ancestry enters the battlefield tapped. {T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Port of Karfell enters the battlefield 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.)

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

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

Shipwreck Marsh enters the battlefield tapped unless you control two or more other lands. {T}: Add {U} or {B}.

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

({T}: Add {B}.)

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

Temple of Deceit enters the battlefield tapped. When Temple of Deceit enters the battlefield, scry 1. {T}: Add {U} or {B}.

{T}: Add {C}. {T}: Add {U} or {B}. Underground River deals 1 damage to you.

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.

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.

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

Whenever you draw a card, each opponent mills two cards.

Landfall — Whenever a land enters the battlefield under your control, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

As Sewer Nemesis enters the battlefield, 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.

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

Whenever a creature dies, put a charge counter on Black Market. At the beginning of your precombat main phase, add {B} for each charge counter on Black Market.

Add {B}{B}{B}.

{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.

{1}, {T}: Add {U}{B}.

Multikicker {2} (You may pay an additional {2} any number of times as you cast this spell.) Everflowing Chalice enters the battlefield with a charge counter on it for each time it was kicked. {T}: Add {C} for each charge counter on Everflowing Chalice.

As Herald's Horn enters the battlefield, choose a creature type. Creature spells you cast of the chosen type cost {1} less to cast. At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

{T}: Add {C}{C}.

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

Enchant creature card in a graveyard When Animate Dead enters the battlefield, if it's on the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with Animate Dead." Return enchanted creature card to the battlefield under your control and attach Animate Dead to it. When Animate Dead leaves the battlefield, that creature's controller sacrifices it. Enchanted creature gets -1/-0.

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

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.

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep. You draw a card at the beginning of the next turn's upkeep.

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

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

Flash This spell can't be countered. Whenever you cast a spell, choose up to one — • Return target spell you don't control to its owner's hand. • Return target nonland permanent to its owner's hand.

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

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

Whenever Sludge Monster enters the battlefield 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.

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.)

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.